This is an odd ball because of the narrow center strip.
The finished star measures 4.25" square. To enlarge to a 12" finished size, (or 2.8235 times as big) you are going to wind up with really weird cutting. Like sixteenths of an inch. Can you live with a finished 12.5" block? If so, each of the 4 quadrants would finish at 6", and the center strip would finish at 0.5 inch. The proportion will be a tiny bit off, but you would get the same effect.
If 12.5 finished is OK, the HSTs finish at 3", so cut the squares at 4", make HSTs, then trim to 3.5. The little partial log cabins in the corners: the starting red square is 2", first small white strip is 2"X2", the long rectangle is 3.5" X 2"
the narrow strips are 1" X 6.5" and the center red square is 1X1
If you truly need a 12" finished and want to retain the exact proportion of the one in the tutorial, you are probably going to have to paper piece the HSTS and the Log Cabins, then join. I googled Scandinavian star quilt and others came up, but none were exactly the same as the one in your link.