Using your seam gauge, measure the seam allowance you need to sew, starting from the needle to the right.

Mark the spot for ease of reference (this is optional).

Remove the last page from the post it pad.

Place the post it with the glue side right next to the mark you made on your sewing machine plate and press firmly.

Place the fabric under the foot and push it to the right until the edge meets the pot it.

Start sewing. At this point you only need to make sure the fabric doesn't slip to the left as the right side is secured by the post it.