Well,
I planned this in my way, but I don't know if it's the best way to build a tilt rack...
Anyway, here's my system:
In the picture above (sorry for this very terrible picture but I really cannot use PC for everything that's not music :-) ), you can see the top panel of left basement rack (15U). Its normal depth is 30 cm, then there are two branches going forward for 20 cm more.
Picture below: the left side of the table (same on the right one), is cutted to be exactly the same of the lower panel (rack top). So same thing, 30 cm, 20 cm branches, etc...
Now you obviously have to put the table on the rack top, with glue, screw and whatever.
Let's go to the second picture:
Ok. Start building up a normal rack, cut the wood as you're not going to build a tilt one. Then you have to modify two side panels as in the first image: cut with an angle of 45° degrees (or change if you want different slant) and remember the depth of the cut: exactly 20 cm (like branches' lenght). Do not screw the lower panel of this little rack now, do it after you mount the rack on the table. Just upper panel, and two side panels.
Finally put this rack on the table. Rack edges will fit exactly on table's branches. Align everything left.
I know that my English is terrible so it's hard to understand, but feel free to ask me for more pictures or explaination!