Step 3: Sand and glue the center section
Take a piece of 220 sandpaper and lay it flat on your table. Now, take the first piece of the center segments and look at it. It has two sides that are 1/4" x 3/8". You're going to sand these sides, only these two sides for now. Take the piece and lay it on the sandpaper. Holding it carefully with your fingertips, rub it back and forth on the sandpaper. Keep an even pressure on all sides so that you don't sand a slope, we want it as even as possible.
When you've sanded both sides, put it back and do the same for the next one. Keep going until you've sanded them all, KEEP THEM IN ORDER.
Now it's time for glue. For this step I use superglue.
Take the first segment and wet one sanded surface with superglue. Take the next segment (this is why we kept them in order), and press one sanded surface against the wet surface, line them up as well as you can and hold them, without moving, for at least 30 seconds, until the superglue sets up. Work your way down the line, gluing each one, until they're all glued together.
Now, look at your work. You sanded them as evenly as you could and glued them carefully, and they're still crooked, not to worry.
Get the old 220 sandpaper out again and put it flat on the table. Now look at the piece, it has two ends, 1/4" x 3/8" and a top, 1/4" wide by however segments you used. We're going to work on the 3/8" x 1 1/2" sides. Lay the piece on the sandpaper and sand it carefully. You want it completely flat, and you want to get that flatness with the least amount of sanding possible. Now, sand the other side the same way.
Now take the two side pieces that you set aside earlier. Put the center segmented piece down on the table and put a side piece on either side of it.. Look carefully, they probably don't fit together tightly so, sand the side of the side pieces until they fit tightly against the center segmented piece. Remember, the less sanding the better, but we want a snug fit. Now it's time to glue all three pieces together. I use gorilla glue here. If you want, you can use wood glue or superglue. I like gorilla glue because it expands to fill any little gap I may have left. Glue the three pieces together, clamp them and take a break until the glue sets up.