rheauljj - Thanks for the Kudos.

The way I tackle horizontal alignment is to use low-tack double-stick tape to hold the two surfaces together - one trailing edge above the other. Then I draw the hinge locations using a machinist's square.

When I use the Robart guilde I look carefully down the hole to make sure the line is centered. Because you have to look at an angle so you don't block light getting in, the line can look centered when it's not.

I clamp the guide in place using a couple spring clamps while I'm doing this. Then I flip the surface around several times and look at it from as many angles as possible until I'm absolutely satisfied the line is centered. Then I put the bit in and give it one or two turns and remove it. Look in the hole again and make sure the dimple is on the line.

The guide should take care of vertical alignment.

I also drill for the hinges before I do any major sanding. The only sanding I do is to bring everything flush and usually I use stock that's thicker than the piece will end up being. After all the hinge holes are drilled I use dowels to put the surfaces together and I sand them as a group to bring them flush with each other. If you use thicker stock then you can sand the hinged surfaces to a perfect match.

In practice that doesn't always work so well because the next thickness from 1/4" is 3/8" and I don't want to sand 1/16" off each side. So I do the best I can with the hinges and usually end up with a surface that's a little thicker than 3/16"

If I'm building the surface from sticks then I saw my own and I can make them 5/16" thick which I can sand to 1/4".