I basically make a 4x6" or larger section of terrain as a foundation for my bases. I sculpt it up with the intention of making a large silicone pour of it. Once thats done, I pour a thin layer of resin into the mold, and then stick the plastic bases onto it. As the resin sets it adheres to the plastic, and the texture of the terrain is not on top of the plastic. This method takes a little more effort to set up. But has a couple of benefits over individually molded bases. First- your bases dont all come out the same. You can add variation by changing up where you set the plastic bases on the resin. Second- it works for multiple sizes of bases. 25, 30, 40, 50, even the big 120's and flier ovals if your original terrain mold is large enough.
Now that I can crank these out, I have one less excuse to get to finishing my Tallarn army. So thier might be some movement on the GW front- if I can pry myself away from the Waramchine...
Also- if these look like something you might want to use as bases for an army project, feel free to get in touch. Id be happy to work out some trades or even sell some if it helps someone get enthused about thier army :)