I would probabyl cut the design square, starch, and block it so it is square

I've cut out many panels and haven't worried about it too much. Maybe I should! I've just added a stop border and it seems to make it look ok. I will watch more carefully in the future!

great advice from all of you... my project for this afternoon is to cut placemat panels that I purchased at a quilt show and haven't even layed them out yet to see if they are going to be square on the cutting mat.

I soak mine with heavy starch and block it first!

I have cut mine out with as much of a border as possible -- then add an additional border and then cut the block straight. No one seems to notice if the outer border is a bit uneven.

I had a laugh to read that "some" panels are not printed square. I have yet to find one that has been!

I use Sta-flo starch, 1/2 starch to 1/2 water, and dip the panel in that and let it drip (don't wring it out!). Then I block it, which is the same as others have been telling you: pulling and pinning it square and letting it dry.

It's not just the panels. There is a lot of "unsquare" fabric out there. I tried to make straight borders by ripping the fabric instead of cutting, on a fabric I thought I had squared. It's usually how I do it to get them straight. But trust me, even that doesn't always work. If you mess up your yardage making borders and they're wonky, it can get expensive!

I bought a fall harvest fabric at JAs and it was printed so crooked on the grain that I lost nearly 8" out of a yard to get the pumpkins to line up for an edge. Grrrr. On my next trip back they had a brand new bolt out and it was just as bad as the first.