My sink (DIY fibregalss over 3/4" plywood, I made 24 years ago now) sits on a frame of 2x4's. There is a shelf half way up on the underneath that does not come out full depth, so you don't bang your knees. The legs are made of a length so that I don't have to bend at all to work on prints in trays if the trays are at the front of the sink. Under the sink I have racks that hold print drying screens on one side. On the non screen side, the shelf holds 4x5 tanks, and small trays, as well as my magnetic stirrer.
The floor under the sink holds gallon glass jugs, and other large liquid jugs. Otherwise, liquid solutions sit on 8" deep shelves that attach to rails affixed to the wall behind the sink.
I wish I had your luck of a sink that is capable of 16x20 trays. When I go that big I go to the tp of the washer and dryer next door in the laundry room.