A: Yes, it can be attached on top of the tiles.
A: Per the installation instructions, this soap dish is designed to attach to the backer board or void where an original soap dish would have been tiled in. The front of the dish does contact the face of the tile and is meant to be grouted around the perimiter after installation. In my case I use a kitchen and bath adhesive sealant to seal up the perimeter because it had a much shorter cure time than grout.
A: Valued Customer, Yes the groves are sloped to keep a soap bar from sliding out.
A: No. The shelf is flat, the soap does not slide.
A: Hello Debbie, The soap dish is installed using mortar or thinset if done while doing surrounding tile. I have also seen them supported with a construction adhesive in the cases where they are installed as a repair. I hope this helps. Cheers, Chris
A: I use liquid nail
A: Purchase an adhesive that will work on ceramic products and is waterproof. Make sure the surface is completely dry, even clean it with alcohol and dry cloth. Read the instructions, tape it to the tile and do not touch for 24 hours. Then apply caulk to the entire edge. Looks great.