1) Choose your fabric.
Lena Fabric, Ikea.com
The reasons I would go with Ikea textiles are many. First off, they're affordable. Second, I love the design aesthetic-- I like a more modern/danish/scandinavian approach to home decor, than the more traditional patterns and designs you might find in a regular fabric store. Whatever you end up picking however, I suggest going with a large graphic print, to fit the larger frame-- it makes more of a statement, and it's easier on the eye. The fabric should be a 100% cotton and the weave a little more course than a fabric you'd use for a blanket for example. If you don't buy fabric often, you should know that when it's on the bolt, it's actually been folded in half. Most home textiles come with a fixed width of around 60." (Double check when you're buying though) For our wall art, we bought a yard of each.
2) Make your frame.
I picked up 6 6' 1"x 2" peices of lumber at Lowes for a decent price. I had Lowes cut two of the pieces in half (3') for me. Then I got my dad to cut the edges into mitered corners.
Illustration courtsey of kombat.org
I put down the lumber in the pattern of how I wanted the frame to be put together. Using a triangle and a pencil, I measured exactly 45 degree angles on each of the corners. It helps to visualize in your head a frame with corners like this (almost all frames have these corners) that you've already seen. Then I got my dad to use his table saw to slice along the pencil marks. Once the lumber has been cut to the angle, be sure and not touch the ends to the ground-- the sharper the angle is, the easier it fits together.
Next I got my husband to fasten the frame together-- his parents had a framing and painting restoration business and so he was pretty familiar with how to make a frame. Using a staple gun, he put staples perpendicular to the 45 degree angle, to hold the two pieces of wood together, then took one nail and secured the corner from just one side, for each of the four corners of the frame. I think it's easier to put one corner together, then the opposite corner, and then fasten the two pieces together.
3) Stretch the fabric.
Be sure to iron out as many wrinkles as possible. Even though you're stretching the fabric over the frame, a crease (and wrinkles) will show. I suggest using a clear starch, like Mary Ellen's Best Press (seriously, the best thing since the iron for getting wrinkles out of ANY fabric.) and the steam setting on your iron to get any offending creases or wrinkles out.
Lay the fabric down on the ground and smooth it out as flat possible. Take the frame and center it over the pattern appropriately. In hind sight it would be helpful to have a second set of hands to help get the material as taut as possible around the frame.
Photo courtsey of howaboutorange.blogspot.com
Stretch the horizontal edges first. Have someone else hold the fabric on the opposite end as you, then take your end, and pull as much of the fabric as possible over the backside of the frame. Be careful not to create vertical ripples across the fabric by pulling hard. If you do, before you start stapling, just pull a little on the vertical ends of the fabric to get those ripples out-- again the object is to pull as tight as you can, while keeping the fabric as flat as possible.
Staple as close as you can to the inside of the frame-- this will keep the fabric tight as it goes over the edges of the frame. Staple both of the horizontal edges first, then stop and get ready to fold the corners and staple those first before stapling the vertical edges last.
The object of the corner, is to have as little of the fabric showing by creating a very flat fold across the bottom and top of the frame-- much like a hospital corner on a bed, or gift wrapping a present. Take the corner fabric, create diagonal fold (think triangle), then wrap the fabric across the bottom (or top) of the frame. It'll look like a small flat triangle.
Then fold the remaining fabric onto the back of the frame. Position the excess fabric from the corner to lay as flat as possible with the vertical portion that you haven't stapled yet, pull tight, and staple. Do all the corners first, then staple the remaining fabric on the vertical sides and trim the excess.
Ta-Da! I realize that last bit is confusing without pictures, but honestly, once you get to the corner wrapping part, it shouldn't be that hard to figure out.