Wet the board with water.

Put a dry Tenugui on the wet board.

Press hands through the Tenugui to stretch any wrinkles.

Spray water starting from center to outside edges.

Slide hand to smooth the wrinkle on wet spot by pushing any air bubbles out.

If there's not enough water, there will be wrinkles.
Make sure to spray water to wet the edges.

After wetting the entire Tenugui and removing wrinkles,
put it in the frame while it’s still wet.

Put the backboard on the frame.

Done!
Please hang it on the wall after letting the frame dry completely for about half a day.