The answer is Hill Helpers™! Needless to say, that's not really a trademark, and I'm not selling them- they're just wooden blocks: little blocks of wood the right size to support the dangling edge of a precariously deployed unit.
I started off with 25mm cubes of pine, bought fairly cheaply on eBay. I bought them here.
With PVA I glued three together, and another pair, and along with a single cube, I sanded them all down to give smooth rounded edges and corners that were comfortable to hold, and then oiled them very lightly with olive oil.
The three Hill Helpers together fit very nicely into a spare compartment of the box I use for dice and counters etc. for Kings of War.
I could have made them look more like terrain, but I chose to keep them looking like this because I worry that I'll absent midedly leave them on the battlefield and treat them like terrain if they look like hills. Also, they should last years and years like this with very little upkeep, and I rather like the way they look, and they're pleasing to hold.
Hill Helpers in action: