I compiled a list of what size square to start with to achieve a certain finished HST size. Some of them may have been a little more accurate if measured to the nearest 1/16" in, but the nearest 1/8"in should get you pretty darn close.
For finished size: Cut:
1.0" 1 7/8"
1.5" 2 5/8"
2.0" 3 3/8"
2.5" 4"
3.0" 4 3/4"
3.5" 5 1/2"
4.0" 6 1/8"
4.5" 6 7/8"
5.0" 7 5/8"
5.5" 8 1/4"
6.0" 9"
So next, sew 1/4" seam around all four edges of the squares right sides together.
If you pivot at the corners, your open seam pressing later will be much easier. Finish the last side off by crossing over your initial seam.
Here is the finished square with all four sides sewn.
Cut on both diagonals using the 45 degree line on your ruler and your rotary cutter.
And shazam! You have 4 HSTs that need zero to minimal trimming and require just a little zippy sewing. Hope this is helpful! I used this method while making my next Farmer's Wife block (number 7 in the book) and my 1.5" HSTs turned out perfect!

