K this is how I used to do it. As I work in scrappy mostly I don't really do alot this way anymore but if you are doing a bunch of the same fabrics this is a quick easy way to do them. I actually started out seaming the strips on both sides and laying the template on the seam and only cutting out one half of the triangle. This works ok but I felt I had better accuracy with the strips open. Both would be fine to use. This is actually a bit quicker to do. But you do have to clean up the squares sometimes from dogears on some of them.
Seam on both sides
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Cut one triangle from the seam on one side then place the template on the other seam and cut out.
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Here are the HSTs from the strips
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