Next....cut 3 7/8" & 2 1/8 " squares on diagonal to make 4 half square triangles of each. ( I startch pryor to cutting due to bias edges created).
Use one large HST and stitch 1/2 way across one edge of center. Lift aside from unstitched end. Place a 1 3/4" x 6" strip along edge and sew to approx 1/2 way mark.