How do I DIY these floating wall wooden ledge shelfs? Look like crown molding shelfs? How to hang?

the wood pieces are run through a table router or a hand router that has a special " router bit" is pushed along the board edge and cuts the special edges. see if you can find a local cabinet shop or wood shop and maybe they can show you. or find some handy person who might have one. "Routers" are all around you. In the old days before electricity, they did them all by hand.