I have had a request to provide pictures of the back of my POTC blocks to show how they are pressed. You can see my piecing method in my May 2013 posting, and a lot of my individual POTC blocks in the February 2013 posting.
This piecing method (stopping at the seam intersections) allows the seams to open at the intersections in a swirl. The result is that the seams and intersections lie very flat, without the bumps intersections usually have. Hopefully the pictures will be clear enough that you will see how they are pressed. Note that because this is hand pieced, we do not press the seams open.
Although I do not consider this block to be as pretty as some of the ones I have made, the picture of the back of it was the clearest to see the seams, intersections, and swirls.
The process for pressing these blocks is to wait until the block is complete before pressing, and when you do press, be careful that you do not stretch, or deform, the pieces. If you press while constructing, there is more chance to stretch the pieces, so please wait till the end. This is gentle "pressing" not strong-armed "ironing." Be gentle. :o)
After the block is complete, begin in the center with a swirl right in the middle - just finger press it to get it started. The seams will all go in the same direction to create the swirl. Move to the next round and make the seams go in the opposite direction, creating swirls at the intersections as you go around. Continue in this method, making sure the seams in each round go opposite of the previous round. For closer detail, please see the 2 pictures below. It may help you to finger press all rounds/seams before you try to press with an iron. Another option is to use a miniature iron to make each round more accessible.