I created a simplistic key hanger that mounts to the wall using 3M Command strips.

For assembly, there are 4 parts, the base bracket and then 3 hooks. The hooks should snap into the base. I HIGHLY RECOMMEND using a little bit of super glue and gluing the hooks in. The tabs on the hook will hold them in place while the glue dries. Then you can snip the tops off with flush cutters like I did so it is flush on the top.

I designed this to use the small command hook adhesive strips. Something like this. These are long enough that they will adhere to the entire bracket but also have a little bit of the tab hanging out the bottom(see 4th picture) so if you ever want to take it down, you have access. I used two strips and it seems to be pretty strong but if you are concerned, there is room for 3 strips.