This file has 3 canvases.  The first one is for 3mm basswood plywood for the box.  The second and third canvases are for 3mm walnut plywood for the frames.  The third canvas is for the spaces which are not visible in the final product, so you can use any 3mm material.  Just make sure to adjust the settings if the material is changed.  Process your material.  Clean and/or sand if needed.

Glue the spacers onto the back of each frame.  Be sure to line them up with the bottom and sides of the frame as shown in the picture.  Glue your box together.  Once dry, glue a frame to each side of the box.  Insert 3x3 inch photos into the frames and put the top piece in place.  You can now add flowers or a potted plant to the box.