Once the figures are painted and varnished (and the varnish is completely dry!), I fix them to their bases using a hot glue gun. If possible, I prefer to use laser cut 2mm MDF.
Next I paint the MDF with neat PVA glue straight from the pot, making sure that I put plenty around the metal base of the figure to help the figure blend in.
While the PVA is still wet, I texture the bases. This is two stage; first, I have a small pot of Cat Litter (which looks just like rocks of various sizes, but is much cheaper than purpose made texturing). I take a pinch of cat litter and sprinkle it over some (not all) of the PVA on the base. Then, I dip the base in my sandbox and shake off the excess.
Before the PVA is dry, I then brush away any sand that has attached itself to the figure by mistake. I find it helps if the brush is wet with clean water.
Now leave the bases to completely dry
Next is the painting. I only use Vallejo or Citadel paints for the two highlights, for the base coat I use artists tubes because for the same money there's a lot more paint!
My base triad for European battles is
Burnt umber (Reeves Acrylic)
Beige Brown highlight (Vallejo)
Sand highlight (foundry)
Once this is dry, I paint random* blobs of PVA on the base and apply static grass with tweezers, shake off the excess, then I paint more Random blobs of PVA and apply grass tufts. Don't worry if the white PVA shows through, once it dries clear & becomes invisible.
*it is also a good idea to apply static grass to cover up any areas where the outline of the figures metal base is still obvious and not blended in correctly during the texturing stage