When cutting full sheets with my circular saw, I use plastic shelving units as sawhorses. The height is just right and by using three of them, I can make cuts in any direction and the plywood is fully supported. And because the shelving units are made of plastic, I can cut right into them without worrying that they’ll damage my saw blade. Plastic shelves are available for $20 at home centers. — John Tinger. Check out these tips for making long cuts with a circular saw.
This super-strong and simple-to-build workbench is may be the project you've been looking for a long time. You have to select some free workbench plans to create yourself a working table in your shed that after you can use it when you are working on your projects and maybe it can provide you some extra storage, depends upon which plan you are choosing to DIY.