Making a costume top hat requires cutting out fabric pieces according to a pattern, stitching them together and adding heavy interfacing. Construction also requires attaching bias tape to the area where the brim meets the crown.
Print off the pattern according to the desired height, either 20 or 23 inches. Assemble the pattern. Lay the fabric face down on a table, and pin the pattern pieces on the back, cutting them out. Follow the manufacturers instructions to apply heavyweight interfacing to the wrong side of the hat brim, top and crown pieces.
Place the right sides of the brim together. Pin them, and stitch them with a 5/8-inch seam allowance. Trim the seam, and clip the curves. Turn the brim right side out, and press flat. Finish the outer edge of the brim.
Fold the hat band in with a 1/4-inch hem, and press flat. Place the wrong side of the band to the right side of the hat crown, and stitch along both the upper and lower edges.
Place the right sides of the crown pieces together, and stitch together with a 5/8-inch seam. Press, and trim the excess. Place the right sides of the crown and top pieces together, stitching them together with a 5/8-inch seam allowance. Clip the curves, and trim the excess. Turn the pieces right side out, and finish the seams. Flatten all seams.
Match the curve of the crown to the brim. Pin together, and then stitch with a 5/8-inch seam, trimming the excess after. Press all seams flat. Cut the bias tape to the correct length, and stitch it to the inside of the crown where it meets the brim. Press to finish.