Here is the letter Q, with a brand-new how-to! You can click each photo, then click again to get a bigger view. The squares on my cutting board are 1" apart.
I made a big backwards C. I've included my hand near the block, so you can see just how big it is. I am looking for the finished letter to be in the 4" - 4-1/2" size range (10-11.5 cm).
I've sewn a long piece of red to a long piece of white fabric for the tail of the Q, and here I am positioning it. Notice I have allowed for the seam allowance. I'll pull the "tail" piece away, and cut the block apart, then insert the "tail".Oops. Re-do. (Do note, however, I have trimmed the width of the tail so it is quite skinny.)As you can see, the letter is WAY too big. Here's how I judge. I set one of my cutting rulers over the letter and use it as a guide. This ruler is 4-1/2". I want to allow for the bottom seam, but I also need to allow for the top of the Q.
Here I've cut the excess away, but I'll use part of what I cut off as the top part of the Q. This top bit already has the background fabric attached, so that will save me some fiddling.
Now I need to add the piece to the left side of the letter. After working out how wide I want the Q to be, I trim away the excess (always remembering to leave enough for the seam allowance.)
Insert the last strip on the left, and PRESTO!
A nice, new Q!