Crispy, the 4 patch HST's are 5.5" unfinished, 5" finished. With charm squares I made them Jenny Doan's method: put 2 charms right sides together and sew 1/4" around all 4 sides, then cut in half diagonally both ways. I usually don't like leaving myself bias edges like that, but I am having no issues with these blocks. (probably because they are small) You can starch the charms if you are worried about bias. Trim your HST units to 3", then sew them together like a 4 patch, making sure your colors are where you want them. I will set these on point as you see on my design wall.
You can also make your HST's from 2.5" strips if you have those. Place 2 right sides together and sew down both long ends. Use your 45* angle on your ruler and make a bunch of HST's that measure the same as the method above. Trim to 3" units. Again, the edges are bias, so be gentle and use starch if you'd like. I have used both methods here as I had strips and charms I wanted to use.