How To Do Decoupage Under Glass?

First of all, you should take a scrap of paper and then glue it under the surface that you want to paint. Be careful to put the paper under the surface and not on it. Before applying the glue, the glass should be washed properly with a washing liquid and should be dried off with a something clean.

While gluing, you should apply the glue on the glass and not on the paper. After gluing the paper you have to remover the scrap after the glue has dried off and then you need to clean the glass around the figures so that its clean.

After that you have to paint the background and then varnish. You can find more tips and detailed steps on gluing, painting and varnishing. This is a video that would guide you with it.