The tops are built in place & are not removable. The top rings are assembled with glue, placed in a ring jig to support & keep them round while they are rabbeted on the inside & fitted with a plywood disc top. After sanding both sides flat, the bottom round over is routed & is sanded where it would be difficult to sand after assembling to the main body. After the top is glued & nailed in place, the pre-assembled veneer disc is installed, trimmed with around over bit & all is sanded.
The bottoms are built similarly except instead of a solid plywood disc, a plywood ring ring is used. This creates a recess in the bottom for a removable cover. The inside is sealed with a clear finish.
The way I did it was more a labour of love. A faster way would have to be done before they could be produced commercially, as I had hoped.