This is for the Tips and Tricks Section…
Many of us here use the Festi Box website to make our boxes. I wanted to share some key settings I discovered when making some 3D boxes.
URL: Boxes.py
When you go to this website, the buttonology can be pretty intimidating, and can eat a LOT of draft boards trying to figure things out. 
When I create a box, my goal is to have smooth edges and surfaces on all sides. That’s the goal. The reality is slightly different and requires experimentation. I’ve found through trial and error the there are three key settings I can adjust to get the smoothest fit possible:
With most of the box types you choose, there are two sections to make the key adjustments. The first section is the “Settings for Finger Joints”:
Expand the section and look for the ‘Play’ setting. Set this to 0.02. As the name implies, it allows for a small gap (or 'play) around the finger joints. This makes it easier to fit pieces together. If you want less play, use ‘0’ or a number smaller than 0.02. You can also increase the play with a number larger than 0.02. I recommend not going above 0.05. YMMV.
The second section is the “Default Settings”:
Expand the section and look for the setting “Thickness”. Set this to 3.19mm for Medium Draftboard or Medium Plywood. Using my vernier calipers, I found that thicknesses for medium plywood and draft board vary between 3.15mm to as high as 3.27mm. This makes creating boxes more challenging because the material thickness determines the size of the finger joints. I found that a good starting number for the medium draft board and plywood stock is 3.19mm.
The third setting is also in the “Default Settings”: ‘Burn’. Set this value to 0.08mm. I used the “Burn Test” app under the “Parts and Samples” category on the main web page. After a LOT of trial and error, I found that setting the ‘Burn’ to 0.08mm gave me the best overall results. The ‘Burn’ setting is what compensates for the kerf (width of cut) left by the Glowforge Laser.
To recap:
Material: Glowforge medium draft board or plywood.
URL: Boxes.py
Category: ‘Boxes’
Box Types Used: ‘OpenBox’ and ‘UniversalBox’
First Key Setting: “Settings for Finger Joints” >> ‘Play’ >> 0.02
Second Key Setting: “Default Settings” >> ‘Thickness’ >> 3.19mm
Third Key Setting: “Default Settings” >> ‘Burn’ >> 0.08mm
When trying to get a good fit, adjust the ‘Play’ setting first.
When trying to get smooth edges and surfaces, adjust the ‘Thickness’ setting first.
Adjust the ‘Burn’ setting last by moving in 0.01mm increments in either direction.
As I stated earlier, “your mileage may vary”. Do some experimenting with scrap pieces of GF draft board or medium plywood. I usually make my test boxes about 35mm x 35mm x 35mm with ‘outside’ checked on the dimensions.
Hope this helps,
Tracy-Paul