Recently I saw a post (on a Facebook group about board game customization) about making custom Zombicide miniatures. Essentially, the idea is to add a regular sheet of paper in between the front and back of the miniature before cutting. It is a good idea to lightly brush each piece with a glue stick to prevent them from sliding while cutting. This produces a template in the exact shape of the cut mini, which can be glued to a piece of thick cardboard. After cutting it (and peeling off the template) you get three pieces: front, back and the cardboard filler.
In the original post, the resulting miniature was glued to a large coin, but I decided to try this technique to slot the miniature in a plastic base. It worked very well, the mini becomes very sturdy and can be easily removed from the base.
There is some extra work of cutting the thick cardboard, but I think it is worth it, especially for use in RPGs (or board games) with only a few miniatures. I think this could look good with either white or black edges, for 28mm miniatures.