How to level patio slabs on sand & manhole covers?

[Ruggers]

Does anyone have any tips on how to stop patio slabs rocking on sand after its been whacked and screeded, the odd few i have laid down and find a corner ever so slightly rocking so have to lift it and add a small amount of sand to that carner but I dont want it to move again later on.

Also how do you set flags into them special manhole covers that take sets? the slab is 25mm thick and the cover is 40mm deep

 

[geraldthehamster]

Also how do you set flags into them special manhole covers that take sets? the slab is 25mm thick and the cover is 40mm deep

15mm mortar bed?

Cheers
Richard

 

[Ruggers]

Thats what i was thinking but wondered if there was a certain way or if thats it.