Those tea trays are fully handmade by the studio Dilu (check here to learn about Dilu).
The line of trays feature patches attached for decoration only not for preventing leakage. So it will not affect normal use. The surface is uneven with minor sands spreading over all the tray.
All tea trays have some depth allowing you to shower the teapot. As these tea trays are not glazed appearing rough and delicate texture, we advise not washing them with a brush or other hard cleaning tools.