Yes, I find these pieces fit to ground on slopes and even ground:
les ctverec.p3d (forest, square)
les trojuhelnik pruchozi.p3d (forest, triangle, continuous)
les trojuhelnik.p3d (forest, triangle)
and
les_su_ctver_pruhozi.p3d (forest, square, mixed type)
les_su_trojuhelnik (forest, triangle, mixed type)
Planck