Lift the mattress off the box springs. Be careful not to let it fold, as this may damage the coils inside the mattress. This works much better when two or more people lift the mattress.
Lay material that matches the size of the sleeping set down on the springs. This can be a sturdy piece of felt, burlap or a wool blanket. Another option is to lay sheets of non-slip liner that you would use in a kitchen cabinet in each of the corners and in the middle of the bed. A non-slip pad designed for use under an area rug will also work.
Place the mattress carefully back on the springs.