1. Build top frame attached to wall and temporarily supported level.
2. Individually measure/cut/install legs, which go right from the top of the stand (inside the frame) to the floor.
3. Build bottom frame around legs, frame sitting right on the floor like yours.
4. Individually measure/cut/install pieces laminated to legs, sitting on top of bottom frame and supporting bottom of top frame.
Harder to describe than to do. I will take a couple pics and then see if I can overcome my technophobia enough to figure out how to post them.
