I made four of these coasters for my room, and I use them all the time. Below are the ones I made. They are so simple, and work really well.
I like to use a cutting board and blade or Exacto knife when I do this.
You will need three colors of duct tape.
Cut:
Four 4 in. strips of two colors for the woven part.
Four 4 in. strips of the last color. These will be for the border.
Two 5 in. strips. It doesn't matter what color these are.
Two 4 in. strips on one of the colors. Your choice. They will be for the back of the coaster.
Take one of the weave 4 in. strips, and fold one side in, then the other side. This ensures the edges are clean. Repeat with the rest of the weave strips.
Lay one of the 5 in. strips sticky side up. Then lay four of the weave strips on it about 1/2 in. from each end, so they are right up against each other. Make sure the strips are all the same color.
Do the same with the other color of weave strips.
Lay the two strips on top of each other. Make sure the edges of the top strips meet the place where the bottom strips come off the 5 in. strip.
Weave the two together.
Place one of the strips for the border, longside, halfway down the first row.
Fold it over, so it is longer on the backside than on the front side.
Repeat with the other three sides, taking off your 5 in. pieces of duct tape as you go around.
Flip your coaster over.
Lay the last two 4 in. pieces across the back so it covers the woven part there.
Enjoy!