That would work, but if it were me, I would take a ride to my LFS and buy some live rock rubble off him in the 2-3" size and create a natural looking pocket that extends all the way to the glass and then fill it with sand, you could also get some very coarse sand, I used Caribsea florida crushed coral dry sand. I mixed a 10lb bag throughout my sand bed.
Think of it as building a live rock retaining wall with pieces the size of Lincoln logs or those mega block legos. I would make sure the area you enclose is at least 6" x6" and a full 3" depth. You can taper it so it looks more like a mound than a vertical shelf. Then add a couple pieces of rubble on top to make it look natural. If one is large enough to span the mound and be supported by the walls, and is about 2-3" wide, that would be perfect because it gives your little guy a roof to work with and he will be very happy. Then target release him when you put him in the tank. maybe take a plastic cup that is clear, drill some holes in it, place the cup over the mound with him in it so it isolates him and he has to dig there. it will take him about half an hour to 45 minutes to dig a burrow deep enough for him to disappear in then remove the cup.
It's a little elaborate, but sounds like a fun project to me.