"......I had wanted to get triangles cut before the surgery, but since I didn't I am just sewing straight seams. ...."
I have the perfect method for you. I taught this in my quilting class and everybody loved it. I may have learned it from Eleanor Burns.
Take two squares of fabric (different colors) & place them right sides together. I suggest starting with 13" squares.
Then draw diagonal lines corner to corner. Remember: X marks the spot.
Then sew 1/4" on both sides of the lines, for a total of 4 straight seams.
Fold the sandwich in half, forming a rectangle, and finger press each side. Open & fold the other direction, forming a rectangle & finger press the sides again.
Open out, & using your pressed lines as a guide, use your rotary cutter & ruler, and cut in half. Turn the cutting mat & cut in half again. You will now have 4 quarters with a diagonal line & 2 rows of stitching.
Now cut along the diagonal line right between the stitching.
You will now have 8 half square triangle blocks. Press and trim to desired size. The largest size you will get from these is 6." Most people like to trim them to 5.5."
My rule of thumb for sizing (the fabric squares that will be sewn) these is to figure out what I want the cut size to be (say 6 inches), then double it and add 1 to 2 inches, depending on how accurately you normally cut. If cutting and sewing 1/4" is not always easy for you, then add the 2."
I like to add in enough 'fudge factor' that the results will work every time.