zfs create yourpool yourdevice
zfs set mountpoint=none yourpool
zfs create yourpool/constructor
zfs set mountpoint=/constructor yourpool/constructor
cd /constructor
pkg install SUNWdistro-const
cp /usr/share/distro_const/slim_cd/slim_cd_x86.xml ./
vi slim_cd_x86.xml (and change rpool/dc to yourpool/constructor)
distro_const build ./slim_cd_x86.xml

output should be:

/usr/share/distro_const/DC-manifest.defval.xml validates
/tmp/slim_cd_x86_temp_1209.xml validates
Simple Log: /constructor/logs/simple-log-2009-06-08-11-55-40
Detail Log: /constructor/logs/detail-log-2009-06-08-11-55-40
Build started Mon Jun  8 11:55:40 2009
Distribution name: OpenSolaris
Build Area dataset: maxtor80/constructor
Build Area mount point: /constructor
==== im-pop: Populate the image with packages
Initializing the IPS package image area: /constructor/build_data/pkg_image
Setting preferred authority: opensolaris.org
        Origin repository: http://pkg.opensolaris.org/release
Verifying the contents of the IPS repository
Installing the designated packages
Uninstalling the designated packages
Setting post-install preferred authority: opensolaris.org
        Origin repository: http://pkg.opensolaris.org/release
==== im-mod: Image area modifications 
==== slim-im-mod: Slim CD Image area Modifications 
0 blocks
WARNING: Failed to parse default value `??????????? ?????? ;gtk-theme-selector.desktop,???????????? ??????????? ???;default-applications.desktop,??????????? ????;gnome-cups-manager.desktop]' for schema (/schemas/apps/control-center/cc_actions_list)
WARNING: failed to parse type name `str'
WARNING: invalid or missing type for schema (/schemas/apps/packagemanager/preferences/remote_search_error)
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
gtk-update-icon-cache: Cache file created successfully.
235264 blocks
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==== slim-br-config: Slim CD boot root configuration 
==== br-config: Boot root configuration 
==== br-arch: Boot root archiving (64-bit) 
387296 blocks
273136 blocks
==== br-arch-32: Boot root archiving (32-bit) 
387296 blocks
200640 blocks
==== slim-post-mod: Slim CD post bootroot image area modification 
==== grub-setup: Grub menu setup 
==== post-mod: Post bootroot image area modification 
Warning: creating filesystem that does not conform to ISO-9660.
Warning: creating filesystem that does not conform to ISO-9660.
==== gen-slim-cont: Generate Slim CD image content list 
==== iso: ISO image creation 
Warning: creating filesystem that does not conform to ISO-9660.
Size of boot image is 4 sectors -> No emulation
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Total translation table size: 2048
Total rockridge attributes bytes: 31523
Total directory bytes: 200704
Path table size(bytes): 1282
Max brk space used 84000
369210 extents written (721 MB)
==== usb: USB image creation 
/dev/rlofi/2:   1771800 sectors in 2953 cylinders of 1 tracks, 600 sectors
        865.1MB in 185 cyl groups (16 c/g, 4.69MB/g, 2240 i/g)
super-block backups (for fsck -F ufs -o b=#) at:
 32, 9632, 19232, 28832, 38432, 48032, 57632, 67232, 76832, 86432,
 1680032, 1689632, 1699232, 1708832, 1718432, 1728032, 1737632, 1747232,
 1756832, 1766432
1476240 blocks
Build completed Mon Jun  8 14:14:43 2009
Build is successful.

then:
# echo $?
0

then:
# ls -alh media/
total 1.5G
drwxr-xr-x 2 root root    4 Jun  8 14:12 .
drwxr-xr-x 5 root root   23 Jun  8 14:12 ..
-rw-r--r-- 1 root root 722M Jun  8 14:12 OpenSolaris.iso
-r--r--r-- 1 root root 866M Jun  8 14:14 OpenSolaris.usb

to rebuild just the iso afterwards:
distro_const build -r iso ./slim_cd_x86.xml

to start by default the livessh option, edit the slim_cd_x86.xml manifest, find this snippet:
                        <!--
                             Uncomment before using
                        <title>Special Grub Title Text</title>
                        -->
and after it add:

                        <default_entry>3</default_entry>

(but then it doesn't suffice to rebuild the iso, you should rebuild from an earlier stage!)

More customization:
cp /usr/share/distro_const/slim_cd/slimcd_bootroot_configure /constructor/
then edit slim_cd_x86.xml and change:
<script name="/usr/share/distro_const/slim_cd/slimcd_bootroot_configure">
in
<script name="/constructor/slimcd_bootroot_configure">
then edit slimcd_bootroot_configure and change jack to your username on every istance found in the file.
then edit slim_cd_x86.xml and change:
<base_include type="dir">jack</base_include>
in
<base_include type="dir">yourusername</base_include>

then:
mv /constructor/build_data/bootroot/jack /constructor/build_data/bootroot/yourusername
edit /constructor/build_data/bootroot/etc/passwd and /constructor/build_data/bootroot/etc/passwd/shadow and change jack in your username
edit /constructor/build_data/bootroot/etc/ssh/sshd_config and change PasswordAuthentication to no and AllowTcpForwarding to yes
create /constructor/build_data/bootroot/yourusername/.ssh and put in your authorized_keys file and chown -R the dir to 65432:staff and chmod it 0700

finish studying the /usr/share/distro_const/bootroot_configure file to make those last changes persistent
http://dlc.sun.com/osol/docs/content/2008.11/DistroConst/scripts.html