I built a frame outta 2x4’s, four foot wide by about 12 feet long. I added 2x4 “floor joists” on 24” centers, and covered the structure with plywood for a floor. I attached one of the long sides to the wall, top edge four foot off the floor. I securely fastened it to the studs, then added three legs to the opposite long side.
The bikes on top go nose in to the wall, back tire suspended. Bottom bikes back in so the handlebars and mirrors don’t interfere. I put em on the stand and slide them back against the wall.
I have a ceiling hoist, so getting them up top is easy. Shop’s a mess at the moment, but you get the picture.