This unit calls for 2.5" X 4.5" rectangles, cut in sets of 4 per fabric if you are doing scrappy. Cut 48 sets of 4 rectangles, for a total of 192.
(And yes, you can have duplicates, but just keep them in sets of 4 :c) )

To go with these, you will also need 592 2.5" neutral squares. 384 of them are for this step, the other 208 come later! (But you might as well cut them at the same time, right?)

*NOTE* You will notice there is NO direction for how MANY strips to cut here to get your 592 2.5" neutral squares. I am working from scraps at this point, and all strip lengths are different. The most important thing here is that you cut enough strips to get your 592 2.5" neutral (background) squares.

This is one of those steps where everyone has a favorite method, and you are welcome to do them in which way gives you the best results for you. There are tools out there for taping to your machine bed, or sticking on the bottom of your pressure foot to help you sew from corner to corner across the diagonal of a unit. Some people put a line of tape straight out from their machine needle to help. Try them, try them all! find which one works best for you.

Personally, if a square is 2.5" or larger, I have a hard time sewing a straight line and getting the results that I want unless I draw a diagonal line. This is something I do with a little lap desk while I'm watching TV on the couch in the evenings, just a bit of prep work. It took me one chick flick movie on the Lifetime Movie Network to mark a diagonal line on the back side of my 384 2.5" background squares. Do them in sets, do them as you need them...just do them. :c)
All of the diagonals on these diamond units go the same direction. There are no mirror image units.  Place a background square right sides together with a red rectangle, aligning the edges at the top.  Stitch from corner to corner on the line as shown. I chain piece these all in one chain, keeping them in sets of 4 per fabric.

At this point it is up to you whether you want to save your "bonus" units or not. I, of course, LOVE THESE. I love to get use out of every inch of fabric I own, so this is what I do...as shown in the second picture above.

I sew a second line 3/8" from the first seam line, toward the corner. To do this, I switch machine feet, because on my machine (Bernina, 1080) replacing my 37 foot with the '0' foot allows me to sew that second seam 3/8" away...the foot is just that wide from needle to edge. It is very fast to continuosly sew that second seam when the pieces are already attached by the first seam.  I then clip the threads between, and since I am a scissor gal, I just clip between the two lines of stitching on each rectangle, make one pile of bonus triangles for later, and a pile of rectangles ready for pressing.  Press the seam allowance toward the background corners, being careful not to press the rectangle out of shape.

What I suggest you do is test whether the side of your presser foot will give you the distance that you need between the seams. It might be with your machine that you need to move your needle to the right to get that 3/8" that you need. Remember that 3/8" is MORE than 1/4", but less than 1/2". This gives me a useable size bonus triangle that I can square to 2". If I went with a wider seam in between, I'd have to trim my squares down to the next useable measurement, which would be a wierd number like 1 3/4". Not a user friendly size if you ask me!
Now repeat the process for the opposite bottom corner using the picture at the top of this page as a guide for placement of seam. As with the first diagonal seam, match squares to bottom of rectangle with right sides together and stitch all diagonals by chain piecing. This picture shows all the units piled up in one continuous chain behind my machine! Sew the second seam 3/8" from the first seam toward the corner if desired. Clip threads between units and cut between the seam lines on each rectangle. Set the bonus triangles aside, and press the seam allowance toward the background corners, being careful not to press the rectangle out of shape. Stack in matching sets of 4 and set aside for later use.