I started with a top and bottom circle cut on the bandsaw with a tilted jig to get the angle. I connected the circles with an x up the middle to transfer the load directly downward and eight additional ribs around the outside.
I cut a section out of the bottom circle to allow access, so I could screw through the top circle into the the top frustum to make the hourglass
I used a similar method for the top one, this time using 16 ribs radiating out from a central column. though the ribs appear short in both dimensions, by the fourth layer of 1/8" balsa ply it will be pretty much spot on.
skinning this one was trickier, as the balsa ply really only wants to bend across one dimension and I was forcing it to contort across several. This photo is a good look at how it would bend fine up the center of each slice (4 per layer) but towards the ends it would fight back and try to buckle. The obvious solution would be to break it into smaller slices but at the cost of more time and materials I decided to just go with it.
clear view of the four "slice" layout. I staggered the seams on each layer to keep the curve as smooth as possible. rather than trying to taper the last layer down to nothing I ended it short, and used bondo to finish the curve.
here you can see the purple bondo line fairing out that taper. because the top (big) circle was made from 1/2" MDF and the final edge profile was 1/4" there was a slight ridge which I carefully beltsanded fair. a little about veneering this odd shape
Soaked with bleach (to the point where it lifted my seams) then stained a satin blue-gray. I actually like the color but again, I hate to see the grain washed out. Capped with a beautiful chunk of marble.