I'm in love with layered mattress pads.
Doesn't this look so dreamy
So I got to thinking and realized a pretty mattress pad could be made.
Gather you chosen items, begin by measuring your topper and your sheet. You will be sewing a very large pillow case, that you will be sliding the topper into. You can use your sewing machine to close the open end. You can also add a zipper so the sheet can be washed. I have not tried this but it seems very feasible.
Here is a great DIY for making a pillow case, but of course yours will be large.