Fully unzip the sleeping bag so it lies flat. Fold the right and left sides inward until they meet in the middle.
Cut the ribbon into four 6-inch lengths. Fold one of the 6-inch ribbons in half, and position it at one of the sleeping bag's new corners. Sew the loop to the sleeping bag, and repeat for the other three corners.
Hang your hammock's ridgeline between two trees. Loop a 6-inch loop of paracord through itself twice at one end of the ridgeline, forming what is known as a Prusik knot. Pull the knot tight, leaving a small loop hanging from the ridgeline. Do the same with a second loop on the other end of the line.
Lay your hammock on the spread-out sleeping bag. Fold the grosgrain loops inward, and clip each pair together with two carabiners, one at the head of the sleeping bag and one at the foot. Hang the hammock with the underquilt wrapped around it. Connect the carabiners to the Prusiks, and adjust them for the best fit.