Hi Aggi,
I am presently making a 4 patch posie quilt. I found that choosing the fabric was the hardest part. The instructor said that we needed at least a 12 inch repeat. I found fabric that had a 26 inch repeat. This allowed me to cut 6 inch squares and when the 4 blocks are sewn, it measures 11 1/2 inches.
DO NOT wash the fabric because it will be distorted in pressing.
Cut the fabric in half, lengthwise, using 1/2 for the squares and the other 1/2 for borders. You need to find your repeat. You don't square up the first edge because this will let you know which piece is your cutting piece, or template. You place the first cut on the fabric and line it up so it matches. When you have all 4 pieces cut, you place them on top of each other and use the flat headed pins to hold the 4 pieces together. Place the pins so you don't cut over them with your rotary cutter, like I did.
Decide on the size you want your cut to be, it will depend on your pattern repeat. Because my repeat was 26 inches, I was able to cut 6 inch strips and then cut those strips into 6 inch squares. You will be cutting 4 squares that are the same with each cut.
I was able to sew all the squares, twelve, in about and hour or two.
I hope that this is helpful to you.
Blue Bell