Basic components are a GW 40mm round base, a lid from static grass (any would do), a bit of rod that fit nicely within the hole in the underside of the GW base and some thick plasti-card (mine was about 2.5mm thick and was left over from basing 15mm Napoleonics).
My most useful tool is a compass fitted with a small blade. I picked this up cheep at a hobby store.
I marked the card with the sizes of both the lid and the base. Note how I marked the position of the centre so that I would not lose it. I had to chamfer the outer circle to match the shape of the lid. A small file and thirty seconds later and that was done.
I drilled a small hole in the centre of the lid with the large pin vice. GW helpfully mark the centre of their lids.
The rod is fed through and glued in place. I used superglue for this. Once dry I trimmed with a sharp knife.
The card was then added and we are almost there. Time so-far is about half an hour.
I then added some conveniently sized card counters from a no-longer played board game.
and a bit of sand.
I then cut a bit of card for the centre dial. I copied the symbol on the empire figures because I have an empire army, but I plan to construct a number of centre dials, one for each army and then just swap them over as required.
The centre dial is assembled....
And then the whole lot painted...