You can make the traps as you suggest or like an upside down tent. You can also add a stainless steel or glass rod above the bottom crack because the females often lie over it and can get damaged. I used to make the trap with enough clearance side, bottom and ends in order to easily siphon off waste and catch babies. The bigger you make the setup the easier it is on the fish and yourself. If you make it like a tent, with some practice you can lift the tent,fish and some water and place it in an adjoining tank while you clean the original or catch fry. A couple of solid straps on the trap will keep it off the bottom of the holding tank. A small length of glass or plastic tubing with a hose connected will help in siphoning gunge off the bottom. It is a bit of a mission but plastic tube can be bent in hot glycerine to make it easier still.