Simply tilt the wooden incense holder together with this holder to one side or the other, and the ashes will fall through one of the openings into the container. When the container fills up, open the back door and conveniently empty all the contents to the trash can.
I printed it vertically without supports in Sunlu rainbow silk PLA+ at 0.3layer h, 3 walls, 20% infill. Printed one in PETG as well.
The wooden incense holder that you see in picture is around 260mm x 38mm x 4mm.