I think one layer of 3/4 is pretty thin for a 4x8 table top. I like to use a double layer of countertop quality particle board when I build workbenches. It makes a heavy and strong bench top that will support any machine tools you need to put on it and stand up to any serious pounding you may need to do in the course of your leather work. I glued and screwed the top and bottom sheets together and where I needed a wider top I biscuit joined the edges and staggered the joints. The countertop quality particle board finishes off nice with a router so you can round off all of the edges and sharp corners. I finished mine with two coats of clear polyurethane and after 20 years it has held up great.
Just my two cents...