Start off by cutting a top and bottom piece out of 3/4" particle board using the ShopBot. You will want to verify the sizes of your ballisters and 2-liter bottles and create your own cutter paths, or you can download ours at http://www.lime3D.net/instructables/hourglass.zip
Cut the bottle profile 1/4" deep with a 1/8" end mill or Rotozip bit. The pockets for the ballisters can also be cut 1/4" deep.
For the edge detail we used an Ogee router bit. Because it was the type that has the bearing on the bottom (which we removed), it doesn't cut the bottom of the shape, so we programmed the ShopBot to cut the outer profile the full depth of the workpiece (3/4") first, then followed up with the ogee.
Pay no attention to the other shapes in the photos, as we were cutting three different projects simultaneously.