Nobody can comfortably sleep on bumpy or lumpy mattresses no matter how sleepy they are. There are a number of materials that can be used to get rid of the bumps and lumps.
One of them is fleece. It is warm and cozy and does not come out thus does not require hemming. Two or more layers of fleece are placed together according to the size of the bed and the perimeter is sewn and its good to go. Other material s can be used but they require hemming and may even be quilted to give them an attractive look. The tip for quilting is to add increase the pad by a few inches to allow for shrinkage.
Blankets can also make good mattress pads. It should be cut to the size of the mattress and may be used alone or with another cloth on both sides or one side of the mattress. Old quilts, sheer fabrics of different layers, used sleeping bags, curtains panels stacked and sewed together make good mattress pads.