Huh, you know, that’s a good question. Is the dress in the blog really in two pieces, or is it a print with broad stripes and some clever pattern placement? I can’t quite tell from looking at it.
I think what I’d do if I wanted to look like that, though, is that I’d cut the pattern on the stitching line for the elastic, so there was a top and a bottom half. Then I’d add, say, half an inch to each piece along the edge I’d just cut (so I’d have the same 1/2 inch seam allowances everywhere and not have to worry about remembering a different one). Then I’d stitch the two pieces together, and I’d proceed from there, just following the regular instructions. I think you could probably also stitch together two pieces of fabric and then cut out the single pattern piece, so you’d have it to use again, but if memory serves, there’s a slight curve to that line, so this way might look nicer.
I haven’t tried it though, has anyone else?