Arleners

I do it like QuiltnNan. For your dimensions, you would need two pieces that measure 120 " long x 45" Once you make the tube, you have to match the seams of the tube together. Sort of like when you are folding slacks to hang them up. Then you cut.slit down one of the folded edges. When you spread out the cut edge you have a center panel that is 120" x 45 (minus the seam allowances) with two side panels measuring 120 x 22.5 (minus seam allowances)

I hope that make sense