This tutorial shows how to lay a strong 6' x 3' x 4" concrete slab a foundation for a small structure such as a toolshed or children's playhouse. What's different from this foundation and a simple concrete slab is the inclusion of steel bolts embedded in the concrete that a 2x4 frame plate can attach to. If you just want a concrete slab for other uses (grill, trash cans, etc.) just leave the bolts out in the last step.
I made it in TechShop
. You just need to take the WOD101: Woodshop SBU class in order to be qualified to use all the tools in the TechShop to make the concrete mold frame and stakes. The really nice thing about TechShop is that you can buy the lumber next door at Lowes and walk right into the woodshop and cut it before taking it home.