Just like the start of creating any new component, the spacers started with milling lumber. In this case, both spacers will be made from a single piece. 

With the lumber milled to size, two spacer blanks can be cut from the one piece.

The spacers are then cut to length at the cross cut sled.    

The profile on the ends of the spacers is made using a routing template. The template is made from a piece of 1/2" plywood for the base, with a piece of 3/4" plywood as a backer and support for two toggle clamps. The desired profile is cut into one side. Since both ends of both pieces will receive the same profile, there is no need to have two working sides to this pattern.

With only one side to the pattern, the cuts will be made one at a time. First, the pattern is traced onto one end of each piece. 

The spacers are then rough cut at the bandsaw staying close to, but outside the line. 

The spacer can then be clamped into the pattern and routed at the router table. 

The second end of each piece is then traced and rough cut. 

Finally, the pattern is routed into the second side. 

The spacers will be installed into a dado in the top of the bottom case. The dado is cut using a router with an edge guide. 

A corresponding "tongue" is then cut on the spacer with a dado stack at the table saw. 

The fit is finessed and double checked. 

The ends are removed from each side to give a clean shoulder. 

The upper case will be located onto the lower case using floating tenons are a sort of locator pin. The tenons will be glued into the spacer, but will be free floating in the upper case. They are cut into the spacer using my shop made slot morticer. This could also be done with a router. 

The locations of the matching mortises are measured out and then double checked using the actual pieces flipped upside down on the bech. 

The mortises are routed into the bottom of the upper cabinet using a router and a guide. The mortises are through mortises, so a sacrificial backer is also used. 

Each spacer will also receive two thread inserts which will be used to blot the upper case to the lower case allowing it to be disassembled for transport. Here, the locations are marked out and then drilled at the drill press. 

With the holes drilled, a dowel centering pin can be used to transfer the location to the upper case bottom. 

The thread inserts can then be installed. 

A forstner bit is used to create an oversized recess for the bolt heads. 

The bolt holes are then drilled out and elongated to allow for seasonal wood movement

A chamfer is added to the bottom of each mortise to make locating the correct position a little easier. 

With everything dry assembled, the top can be dropped in place.