I use either 1x2 or 1x3 poplar which I buy at home Depot for the sides of the frame. I use 3/8 x 1 5/8 for the inner part that the panel or canvas will rest upon. I like to use a wider piece for this as I sometimes use Velcro for fastening and a wider surface helps the Velcro adhere better. I do this with the little ones 8x10 and under, as making frames is time consuming and that way I can rotate them easily.
1) Measure the art and add 1/8 all around. Cut the 4 base sections first,measuring twice and cutting once! Glue,clamp, and let dry.
2) Place your art on top of the base and smile at the narrow border that surrounds it! On to the next step.
3)Cut the pieces for the sides of the frame, holding it upright in the miter saw to get the cuts as seen in the 1st photo on left.Measure the INSIDE of the outer frame side to match the OUTSIDE of the base piece and it will fit perfectly. Remember to wear eye protection, hair tied back when you work with power tools.I lay a scrap piece of wood with the 90degree edge on top of the piece to be cut and draw a faint pencil line to mark where I will be cutting. Put the blade down manually to test you are in the right place before you cut. That's the measuring twice part. Cut on the outside of the line or else it will be too short! That's happened many times to me!
4)Glue and clamp the sides using 2 pieces at a time. The top and side together doing that twice. So you end up with 2 90degree corners.
5)Determine what height you need the base to be in relation to the sides so that your art fits in with just a bit of the frame extending above it. You don't want it too deep in the frame, or protruding from it. Use scrap pieces to provide a support for the base while you are gluing the sides together.Check this carefully before you move to the next step.
5)This step puts it all together. You put glue on the perimeter sides of the base and then arrange the side sections in place, gluing the ends of them and clamping it all together. Give it ample time to dry. I use any wood glue.
6) If the frame is larger than 12x12, I would drill small holes at the corners, 2 nails to each side, sink the nails, fill with putty,dry,sand. You will sand anyway when the glue has completely dried. If you wipe any glue overruns off early on, it will save much sanding later.
This has been quite extensive but so many people have asked me how I make frames that I thought I would put it all down. Maybe I should consider making a video to post on my blog. What do you think? I don't know the 1st thing about doing that!!!