Pin exterior squares together, right sides together. Sew a 1/4 inch seam along three edges. Repeat with interior.
Use the seams on the inside to line up your corner. Use a ruler to draw a line that is 4 1/2 inch from the point of the triangle. Sew along this line. Cut the extra, leaving 1/4 inch seam allowance. Repeat for all four corners.
Sew together. Place right sides together (a box within a box) and pin. Sew a 1/4 inch seam, leaving a 4 inches gap for turning.
Turn it right way out. Iron around the edge by using pins.
Finally, topstitch the edge and your fabric bucket is ready!