Turn foundation back over to the blank side. Taking your #2 fabric, place it right sides together with #1 fabric along the trimmed edge of #1 fabric. Just to check, hold your finger along the seam you are going to sew and flip #2 fabric over the #2 section of the foundation to be sure you have allowed yourself enough fabric. I sometimes actually pin the fabrics at the sewing line and flip it over when the section is an irregular shape or the seam is on an angle. Take the time to flip your fabric over its own # to avoid the frustration of ripping out seams and tearing your foundation.
Pin #2 fabric to the foundation, flip the foundation over with lines side up and sew on the lines between #1 and #2, beginning outside the line and ending beyond the line.
Clip threads, remove pin and fold fabric #2 over so that it now covers #2 section of foundation. Finger press seam. Again, turn foundation over to side with lines, place your postcard on the line between #2 and #3, fold foundation over exposing fabric, using Add-A-Quarter ruler, trim a 1/4" seam.
Continue on with your sewing with #3, place and pin your next fabric right side down along the trimmed edge of fabric #2 on side where #3 meets it. Continue on the same as you did above, first checking to make sure fabric #3 covers all of #3 section foundation.
You can press after each time you stitch with a small iron if you prefer it over a wooden iron. You should press with a regular iron every three or four sections and especially when the block is finished. Be careful with how long you hold the iron on as you are working with paper.
Hints & Tips:
Be sure to cut the fabric for each section larger than what you think is needed. It's better to have a bit too much fabric then being short and needing to rip out seams. When you are ready to use a fabric for a section, place it over the # of the foundation and cut so that it is generously larger than needed. You will get the hang of this as you go along. You'll also cut a piece too small a time or two before you learn to be generous enough. We all do!!
Every time you make a fold in the foundation be sure to crease it since this will weaken the paper making it much easier to tear away when the quilt top is complete. DO NOT REMOVE FOUNDATIONS UNTIL QUILT TOP IS COMPLETE INCLUDING BORDERS.