Nina I like to tack my seams together so they can't move. I think tacking is more stable than pins. Just sew a stitch across where the two seams (this is a tack)meet. Sew it where your seam will go aross the fabric. See the picture below.
Make sure the corners on your blocks are square and not off a little. Trim gently to make them square if needed.
I also tack at the sides to make sure the squares stay in place. You don't have to take the tack back out if you put them where your seam will go over the tacks.
I agree sew the first three blocks into a row. Then sew the second row of three blocks into a row. Repeat for the third row. Make sure you tack and check your tack before you sew each time to make sure the seams meet where they should.
Then sew the rows together. Tack where the seams meet and on the ends and you should have a better experience sewing your quilt block together.
I iron all my seams open and I think you can join the seams easier that way. Not so much bulk. You'll have to try ironing them open or to the side and see which is easier for you!
Hope this helps!
This one isn't a four patch but you can see where I tack. Where the seams meet and on the ends where your seam will go through.
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Tack a stitch across where the two seams join. A tack is more secure than a pin.
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