If you are not following a pattern, that closely, it makes sense to work within the borders of the projected finished quilt. That way you have the outline and then you can fill in the middle. Especially if you have a specific bed or wall hanging area you want to complete. Food for thought...smile. The thing you have to understand is you might have to cut somethings off to make them fit. That's okay, you can use them elsewhere. Like all things engineering, quilting has a certain method to it's madness. You have a pattern, you cut the pieces you sew the blocks, attach in rows and then add the borders. That's not how I'm doing my work on this particular pattern. It's quilt is based on Karen Witt's pattern, Tillie's Mosaic. If any of you have attempted any of Karen's patterns, you probably have discovered they are challenging, and I have to say, I like a good sewing/quilting brain stretch, every now and then. It makes me appreciate the simple things like real patterns that you cut out and you get what you want. If you buy the pattern, you'll notice it's unfinished on the front, so, I'm not without some leading indicators that, maybe this ain't the easiest thing to finish.
The pattern as it is, makes a quilt about 60 inches square. I wanted this for a king size bed quilt. So rather than lay it all out on paper, and I'm sure you can find a hexagon grid somewhere on the internet, I chose to begin making the hex blocks and then laying it out on the bed. Next I cut my outer borders to fit my bed, thus, you can see by the pics the fill in areas that are yet to be complete. Believe it or not, I find this to be an easier method for me.