I'd make this in the VM. The pic shows you a quick version. It's made in separate bits. For the bottom part I drew a polyline of the cross section then added thickness of 5 inches. Then I added vertices to the top so that I could change the shape neatly. I selected points at each corner and then moved these down a little. The 'cog' I made by dropping an oval into the VM with a definition of 48. Using Top view I Shift-selected every other vertice. I then scaled by 90% and then rotated a tiny bit. Then I selected all and added thickness of 1 inch. HTH Mark