Help with low spots for shed base

[Ed_Corney]

I've spent various summer evenings and weekends building a shed base in our garden (15x10ft). I've excavated soil, compacted type 1, sharp sand and fitted some plastics grids with 10mm gravel. On final inspection I can see I have a number of low spots in base, where I was clary unable to get the base suffciiently level. They are typcially 10mm, with a couple of 20mm spots where the base clealry didn't compact that well.

How much of an issue will this be going forward, and what's the bets way to recitify it?
First intinct is plastic packers for the shed floor or a supplementary wooden frame for the shed floor which I can level (again with packers I guess).

 

[Tigercubrider]

Pretty much as you say.
You could use slate or tile, but plastic’s as good as anything.

 

[nickjb]

Plastic spacers will be fine. I'd try and use something solid, rather than the ribbed u shaped spacers. Cut up some sheet material.