Step 1: Cut Out Pieces
Cut out the shapes you see above with a laser cutter
Step 2: Glue Pieces Into Platform
Now you'll want to glue the triangular pieces into the platform. I suggest applying a small amount of wood glue to the 2 spots above the lip in the bottom of the triangle.
Step 3: Use Clamps to Keep Triangles Straight
Now you want to use clamps to lock the triangles into place. You'll also want to use the clamps to keep the triangles at a 180 degree position vertically. Do this by putting the small square in between the two triangles to keep them seperated and straight.
Step 4: Finish
After an hour or two, remove the clamps and enjoy your new phone stand.