Hi alikat, I'm back. I hope you are still monitoring this post. Jan from Virginia has a great tutorial in today's board. I surely do agree with your definition of a HST, but this is the definition used by this board. I printed this out, and will find it very helpful. Good luck!
an in VA 
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Here is my tutorial on many different triangles, including the Half Square Triangles you need. It's in pdf. format so you will need adobe reader to open it. That is available free on the internet for download.
As a quick reference, make your base squares ONE INCH larger than the desired half square triangles, then trim them down for better accuracy after sewing them.
Jan in VA
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