Shed Base Advice.

I bought one of those 7ftx 7ft Keter sheds which popped up on here as a deal a few months back and planning to use my week off to make the shed base.

The plan is to make a base big enough for two sheds and then add one more later.

Anyway, I have some old heavy gravel boards left over from when the fence was replaced last summer.

Can anyone please advise if this sounds the right way to go about things?

1. Construct the timber frame and brace it/ put pegs in the ground to support the frame. Make sure it's square etc.
2. put down a layer of mot type 1 and whacker it down
3. DPM sheet down on top
4. put gravel boards on top of dpm
5. Mix concrete and put about 2 inches to level off

Worth putting in a small layer of sharp sand between steps 2 and 3?

Thanks.