I had finished the quilting on this art quilt the other day, done my little happy dance and begun squaring it up when I thought I should record the steps to show you how I do it.
With a traditional quilt you usually have blocks or sashing to line up your edges with. With an art quilt you may not have any straight lines at all. But I usually have a horizon line, or a flying bird shape, or a vertical line that I can get my horizontal line from. Luckily with this one I have a horizon line. It is crucial that the horizon line is parallel to the top and bottom straight edges or it will look 'wrong' on the wall.
Of course, if you want your audience to feel unstable and unsettled when viewing your quilt then go for wonky horizons - but that's a whole 'nother post on how to convey emotions with art quilting!
Take your longest ruler and lay it so the edge lines up along your horizon line or another line that is meant to be horizontal.
Use another ruler (I like my 12 inch square) to slide along your first ruler until you get to where you want your right hand vertical edge. Hold it really steady and make your first vertical cut. Now you have a straight edge to work off.
To get your bottom right corner, take your first ruler away, then slide your square up along your vertical straight edge, until you reach where you want to cut your bottom horizontal edge. I put my large ruler back on top and realigned it with the horizon as a double check. Cut your corner. Now you have two straight edges and a 90 degree to work from.
Slide your square ruler left along your long ruler until you reach where you want to cut your second corner. Hold firm and steady (this is no time to get ruler slippage) and cut again. Now you a nice square bottom (ha!).
Working with your square ruler in the bottom right hand corner, use it and your long ruler to continue the right hand vertical edge.
Continue working your way around the quilt using both rulers to achieve square and straight edges and corners. Use your horizon line, or whatever line on the quilt you first started with, to double check the everything is looking good.
And while you've been merrily cutting away, thinking you'd finished your quilt, keep an eye out for that one thread you missed when you were tying your ends in....there's always one more you didn't find!
And then once it's straight and square and looking pretty, it's time to put it back on the design wall and start auditioning for binding or a facing, or whatever you are using to finish your raw edge.
I hope that was useful and if you have any tips of your own to add I'd love to hear them.