Two cushions are nestled inside a basket, one on top of the other; an electric pet-bed warmer (see Resources, below) sits between them. Any shallow basket will work. This one measures 14 inches wide, 19 inches long, and 6 inches deep. You can make the quilted fabric (see below) or buy it. I used a soft chambray bedsheet for my quilted pieces.
Resources: Fabric for pillows: chambray flannel twin sheet in Bluegrass Chambray (#7674), Garnet Hill; Small pet-bed warmer (KH-002-004), K&H Manufacturing, from Cozy Winters. Temporary spray adhesive by Sulky, Joann. 25 mm Bias-Tape Maker (#464-25), Clover. 88"-by-66" organic wool batting (#2102), Near Sea Naturals.