It’s on some gravel. I was thinking about putting sand under the blocks to be more stable on the 1.250 gravel. It’s spread 2’ in between the 4x4’s here but I’m going to get another and do about 16” or so. There 4’ wide. And I got some 6 mill plastic I wanna lay down or that may not be needed on gravel? I’m going to do 2 slabs wide on this frame.Got this stuff and about 10 more slabs or more to stack