I don't know about perfection but if you use my cut down method and hold the template while you cut you should get the right size every time.
I sew two strips together and open and iron. Then center your template with two corners on the seam and cut around template with a rotary cutter. Go down the strip cutting out HSTs and then pull apart the strips and sew the other side together. Continue to cut out more HSTs. Depending on how wide you cut your strips and how close you can place your template to cut you will come out with a little scrap but not a lot if you make your strips(cewn together) the size of your template from corner to corner on the diagonal. My strips here are wider than the template because I have a fear of making them too small and I don't care if I have scraps left. I just recycle them into more blocks.
sew two strips and cut out squares with template
sew the other two sides together and cut out more HSTs
cut out as many as strip is long