Hello:
In Jennie's video she started with a layer cake, 10 inch square. Cut that into 4ths which would be 5 inch squares. She used the 5 inch squares for the HST and then trimmed to size. Go ahead and try this method as a learning process. The HST are small and the bias may not present a problem. Starch will help. While bias stretches it also eases nicely.
If you require 8 HST of the same color Jan in VA has a good method and it gives straight edges. Still plan on trimming.