That is going to be a large quilt to handle all the way around the bed. Another option is to make a panel skirt for the box spring. They are easy to construct to the size needed. There are 3 separate panels to cover each side of the bed and the foot of the bed. Add a box pleat at each end of the panels.
A 4-6 inch piece of muslin added to the panel piece of fabric. These panels are simply tucked in between the mattress and box spring.