I'm building my sink now. I wanted a sink with sides that I could rest my forearms on while tilting trays and waiting for processes to complete. I tried the height of my studio workbench as a sink base height, 36" above the floor, and found a good leaning depth was about 3 1/2 inches above that, to make 39 1/2 inches. That's the average height. I sloped the sink base so it should drain well. So the sides run from about 2 1/2 at the far end to about 4 1/2 deep at the deep end.
As an aside, I'm in the process, right now, of epoxying the sink together, a bit more of a job than anticipated, but it's coming together. I have discovered I am very good at creating bubbles in the fiberglass. They look horrid. I really hate grinding and shaping epoxy, but, darn it, I'm going to get it faired out well.
I suspect it's a pretty personal decision about sink side height. Some folks like very deep sides and some people put trays on a table.
C