A lot of the joinery in this build will involve long 90mm bolts running through several pieces of wood so it was important to accurately drill straight holes and have everything line up. A drill press would have made this easier, but I don't own one, so I made do with a nice little drill guide from Lee Valley tools. This was easy to use and gave pretty nice results.
Here's the guide:
You start out by using a punch to mark the location of the hole
and then add a 3/16" bushing over that and use it to fit the guide in place and secure it
The you pull out the bushing and replace it with a new bushing sized to the drill bit that you're going to use (1/4" in my case). Using a high quality brad point drill bit also make it easier to get clean accurate holes.