When I was new in the hobby, I didn't mind gluing some figures down to a stand, then just applying some flocking - sure, it looked like the warriors were standing on little grassy lumps, but it didn't bother me.
That was then, and nowadays, I'm a fanatic about trying to disguise the awkward lumps or bumps involved in basing.
Covering those lumps usually involves using some material to smooth out the bumps. I've never found the perfect material, but something I've tried recently is DryDex Spackling.
This material comes in a plastic tub that has a fiendish lid designed to split your fingernails when you try to pry it off. It's spackle, which is a material used to make repairs in walls - in the U.K., I'm told that Polyfilla is somewhat similar - but this product is pink:
So let's try the stuff out! Here I've conscripted the Army for Bill 28mm Ancient Britons, which we last saw mounted onto square slottabases.
Most of these figures were never designed for slottabasing, so some smoothing out of their bases would be appreciated. Two figures, however, are already taken care of!
But this guy, for instance, could use some contouring...