I tried a few different methods but the one I ended up using to cut my material was really basic and simple to do. The first step was cutting out 5x5 squares. Then, using the grid on my self-healing mat, I cut of an angled 1" from each side to make the isosceles trapezoid (yeah, I had to look that up). See the image below:
Step three was stitching the pieces together to form rows, then sewing the rows together which went pretty fast.
And then came creating the back. I didn't have enough fabric of any one color so I pieced together 5" rows. I love how it turned out too. Almost as fun as the front!
I decided to "stitch in the ditch" for quilting the pieces together, meaning I sewed over the seems. Next time, I think I might dare to do some sort of free-hand, it'll be a lot harder, but I think the end result would be really neat.
I forgot to write down the finished size, it's quite small, probably 20x30. Just big enough to play on until the baby starts really moving, the perhaps it'll be a lap quilt for story time!