hmm, don't know if it can be done. If just using a charm pack (5" square), you would end up with 2 HST's at 4.5", with not much waste. So to repeat with fabric on the outer portion, you would have to destroy one of the HST's.
I am doing a Thimbleberries BOM and that is one of the blocks we made for the boarder and will be laying it out in a zig-zag style.