Although 3/8 wall thickness received a lot of support on the prior blog, and Splintergroup graciously outlined how I could get the top set (hope to try that for another project!), I decided to try adding some thickness to the interior on top and bottom of the sides.  The interior was oversized for the temporary plastic urn box so I had room to do so.  Picture of the sides with just the 3/8 thick walls:

Adding to the thickness will allow me to do a simple dado for the top to float and then have good surface to attach the base to the bottom.  Also, like the look of the thicker sides for this size box.

Considered adding a contrasting wood, but decided to just use walnut.  I resawed a piece left over from the board used for the sides and top.  My new Timberwolf blade is working great for me 🙂 and I was able to get three thinner pieces which I got consistent at the drum sander.

I cut bevels on the ends for mitered corners.   

Considered having the added the pieces a bit lower than the box top.

But instead cut a 45 so I can glue it flush to the top.  Looks like a bevel on a thicker board. 

Nothing is glued up yet as I want to make sure I like it after stepping away for a bit.  

Also cut the top to rough oversize. My husband wants a cross inlay.  Showed him various options and looks like maple is the final choice for the inlay,  and splines.  I need to work on the whole inlay process with some test pieces.  Thinking that I need to get the top cut to size and ready for glueup and then do the inlay before actual glueup.  That way, if I mess up the inlay, I'll just need to redo the top.