Garden decking

I would like an area of my garden decked over. Currently the area is covered in a chequerboard fashion with paving slabs and stone chippings. Underneath these are a membrane (presumably waterproof), under which is clay soil. Is it advisable to remove the slabs and membrane before decking? It could of course go on top, but this will create problems with the decking being higher than necessary. I can use the slabs and stone chippings to help fill in an old fishpond so removal of them will not be a problem.