These are the "small" pre-cut terrain bases from East Riding Miniatures. They're 3mm MDF, extremely sturdy and it took me around 3 days to get all 12 bases of foliage complete...
Jungle Foliage - A Quick Guide
1) Sort out the base - mine were ready to go from ERM, but you could cut these out - personally I prefer smaller clumps of foliage, as I use them on a skirmish board rather than a bigger battle board... If you're cutting these yourself, draw the shapes on MDF, cut them out, bevel the edges with a sharp hobby knife and sand the edges to complete.
2) Switch the hot glue gun on...
3) Add rocks/cork/lotus seed pods - I find that doing these first, then spraying with some black undercoat, works well.
4) Add foliage where required. Try and leave space for miniatures - don't clump the foliage too close together. I use aquarium plants for this - separate them up into usable elements.
5) Disguise the hot glue with a filler/sand/PVA glue mix. Allow to dry.
6) Add sand/gravel where required with PVA - allow to dry and undercoat black.
7) Basecoat the sand/gravel (I use Scorched Brown) and when dry, drybrush progressively lighter shades to match your board/miniatures.
8) Add flock.