Place one flue piece on top of the other, with the wrong sides facing out and the right sides facing in. Pin together. You need to pin around all four parts of the rectangle. Place the pins as close to the edge as possible to prevent the edges from coming loose as you sew. Sew around all four sides of the two stacked pieces to create a double-layer piece to work with. You should have a seam allowance of about 1/8 inch (3.176 mm). Lightly fold the flue in half width wise and pin the edges together. Sew along the joined edge using a sewing machine or needle.  Do not iron or crease the fold. Ultimately, you will want this part of the hat to have a rounded shape, not a flat shape. The seam allowance will vary depending on how large your head is. The portion of the fabric leading up to the seam should be about half of the diameter of your brim opening, and when unfolded, this portion of the flue should be about the same size as that brim opening. Release the fold of the flue and try to shape it with your fingers so that the flue shape, as a whole, forms a rounded shape. If there is a crease along the side you folded previously and you cannot get it out simply with your fingers, you could try placing the flue over a round vase, lamp, or similar object to stretch it in that circular shape. Remove the crease by applying steam with your iron.

How would you rephrase that briefly using Indonesian?
Tumpukkan potongan bagian flue. Jahit kedua potongannya. Bentuk bagian flue. Buka lipatannya.