If you’re going to sash the disappearing 4 patch block, it’s not going to matter as much how you iron the seam allowances. But even then, you’ve got 9 intersections where it could get a bit lumpy. So here’s how you get your d4p’s nice and flat…
Here’s your 4-patch from the front and back.
When I sewed the first two squares together, I ironed the seam allowances (SA’s) to the dark squares. When you join the two 2-patches together, you iron the SA’s toward the light squares to make all the SA’s point in a circle, clockwise. Open up the intersection in the same clockwise direction.
The lefthand picture shows, I’ve cut the 4 patch the same distance from the seams (in this case 1.25″) and on the right, you see the centre outside edge pieces turned to create the disappearing part of the d4p block. Now, we’re going to sew this puppy back together.
I sewed the pieces together in rows. The first picture shows them from the front. The middle picture shows each row flipped over to show it from the back. The third picture shows the SA’s ironed and the seam intersections opened up. You start with the middle row and when you open up the intersections, the new SA’s will lie down in a counter clockwise direction. If you look at all the SA’s of the upper and lower rows, they should be ironed the same as the ones in the middle row. When you flip all the rows over again (to the way they were in the first picture in this group), like magic they will be pointing in nesting order. Try it.
These 3 pictures show the rows sewn together. The first picture shows the block unironed. In the middle picture, the block has been ironed with all the intersections opened up. And the last picture is the d4p block from the front, in it’s glory.
And here is the last picture showing that all the SA’s will nest if you sew the blocks together. And if you look closely one block has been turned so that the blocks are not alternating dark and light. No matter how you arrange your d4p’s, all the SA’s will nest and your flimsy will be missing 21 potential lumps: 9 in the middle and 12 at the edges of the block.
Things like this are always very wordy to explain but be assured, it’s very simple.