Go to Lowe's and get yourself a piece of plywood. They have them already cut to different sizes. I think I paid $18.00 for mine. Cover it with insulbrite and batting. I used a staple gun to attach mine. then I sewed a big pillowcase out of muslin to cover it so it would be easily removed to wash. Missouri Star Quilt Company has a good tutorial on how to make one. I asked my fiance to make me one and told him how I wanted it done, but he's an engineer, and they always have a better idea LOL so I did it myself! Good luck!