run a lawn mower over them if you can, or shred them, wet them and bag them up but make sure there are lots of holes in them. do you know what species they are? I find beech and oak take 2-3 yrs to rot down.
sometimes a bit of soil added will also help provide the fungi to get them decomposing.

Beech, birch, oak, Laburnum, possibly a few Holly leaves, Laurel maybe, Hawthorn. You name it, if it grows in the garden the leaves are still here. Leaves may have been in the border for a long time without rotting down, possibly because they are very dry.
No way of running the mower over them. I might shove them through the shredder, if I can guarantee that there are no stones in them.