The bass trap I built (plan on more in the future) was a superchunk design made to look like a shelf. A compromise of quality vs. design. Basically, I cut each 2x4' panel in half, creating 2 - 2x2' panels. Then, diagonal cut to form the wedges. In the corner on top of the baseboard molding I attached a triangular piece of 3/4" plywood using 3/4" strips attached to wall. Then I stacked the fiberglass to the desired height. I could/should have gone to the ceiling, but decided to end at a height that would give me clearance to set a couple of "decor" items on top of. I attached another triangular piece of plywood (pained gloss black) on top. Made a frame using 1" molding strips with black burlap stapled to the back and attached that (molding painted gloss black) to the plywood on top and bottom (like a speaker cover). In fact, it looks like a speaker in the corner of the room. However, instead of burlap, you could use thin laminate and paint it all the same as the wall color. Attach molding across the bottom and you have a bass trap that looks like a built-in shelf.
I used burlap as I wanted the unit to stand out from the room while looking similar to my audio rack in the opposite corner.
I think bass traps can be made quite easily to be disguised more so than other treatments. Hard to hide fiberglass panels attached to walls.