A very important thing when customizing the bases is to close any slots (especially on 30mm and 40mm bases from Privateer Press and similar). All those open slots mean that a lot of glue will get all over your hands/desk/everything else.
Once that is taken care of, It was time to add some ballast to the bases.
Followed by a little sprinkle of sand
One very special base got some more milliput, and it moved completely from the concept I had in mind originally (which doesn't matter since it will become way cooler than originally imagined)
And now it's time for the most exciting part of making bases: waiting for the glue to dry :)