Step 1: Design Your Box Layout
For my purposes I opted for two rows of three, with the row at the back being quite a bit longer than the three at the front so they could accommodate the longer cutlery in my silverware set.
I bought some nice looking 1/4" sanded plywood and calculated in 1/4" inch for each box edge and divider. I was surprised later when I went to piece together my first prototype and discovered that the wood was not actually .25" but was .2" (much like 2X4 boards are actually 1.5X3.5). Be sure to measure the actual stock you're using so you don't get fooled by nominal sizes!
Some design considerations:
1. Having deep, narrow sections makes it hard to get to the bottom of the caddy when you're fishing for the last few pieces of silverware. Consider cutting a notch or lowering the height of the middle of each divider so you can easily grab your silverware.
2. Having some space along the side of your caddy can be convenient for storing odds & ends (like a pair of scissors). If you decide to make the outer border of your caddy smaller than your drawer, it may be worth making the bottom piece extend past the sides of the box so it touches edges of the drawer itself, acting like a spacer to keep the caddy from sliding around.
Step 2: Design Your Wood Joints
Be careful not to significantly weaken any of the boards by removing too much material from any one piece. Removing a large portion of one line or row can also weaken the piece. Notice that the biggest piece in the example has only one block along each edge? That's probably not the best design!
Oddly enough, the smaller you make the fingers of the joint, the stronger the joint will be. This is partly because the glue adheres well to the exposed grain between the fingers, and partly because there is more surface area shared by the interconnecting pieces. It is probably not wise to cut fingers thinner than the thickness of the material you are working with, especially if using plywood. I feel it is a good rule-of-thumb to make the tabs or fingers at least two times the thickness of the box material, and also try to leave that much material surrounding any slots or holes cut into a piece. Leaving too much space between tabs will leave the joint at that area weak and more susceptible to deflection. A careful balance of stability and interconnection needs to be struck.
Step 3: Draw Your Joints in CAD
When translating your idea to CAD, you need to should take into account that a laser cutter does actually remove a narrow channel (known as kerf) from the wood it is cutting, so the piece will be ever so slightly smaller than the line you drew in your CAD program. Unless you account for the removal of this material, you will have gaps and unevenness in your joints. To resolve this, the outside edge of each piece you draw needs to be slightly further out than "perfect", and any rectangles indicating holes to be cut in the middle of a piece (like where a divider runs along the bottom plate) will need to be drawn slightly smaller as the kerf will enlarge the hole. I found that the kerf of the Trotec laser cutter at the settings I was using was about .015", but your results may vary. Make a test cut in your material first before incorporating a possibly faulty measurement into your design.
My solution to this problem was to draw the wooden pieces exactly the size I wanted them in my AutoCAD and then used the 'offset' tool to bump the edge of each piece outward by .006". This gave a very snug fit to the joints and resulted in a very sturdy box.
It may be worth mentioning at this point that long straight vertical lines are much more likely to cause flareups in the laser cutter since the debris gets pulled through the beam of the laser by the exhaust system, so try to lay out your pieces so that the longest edges are horizontal.
Step 4: Cut Your Box!
I recommend making a small test joint file with one finger and one pocket that can be used to test the power/speed of cut on, and use that to double-check that the calculations for offsetting the lines to account for the laser's kerf were accurate before starting to cut my actual project on non-scrap material. Once satisfied with the cut depth and accuracy of your joint calculations, put your good material on the cutting bed and begin the job.
Bonus "Learn from my mistakes" section:
It took me a lot of head scratching before I was able to print directly from AutoCAD to JobControl without having to export the job as a PDF and then print it from Adobe Acrobat Reader. AutoCAD would say the file printed, but nothing would display in the pending jobs. It turned out that AutoCad has trouble printing from a file opened from a usb drive, which prevented the file from printing. Copying my file to the desktop (or supposedly anywhere on the c: drive) and printing from there resolved that problem.
Even after double-checking all of my measurements, I ended up with a few fingers that were to fat to fit into their intended slots. I used a coping saw to remove the extra material. How many mistakes can YOU spot in the picture below?
Step 5: Dry Fit the Pieces
Don't worry too much if the joints are a little stiff when dry fitting them. They'll slide together better once they have glue on them. You may snap pieces when dry fitting joints that are too tight, though, so be realistic about whether or not your pieces fit together properly.
As you fit the pieces together, take note of the order in which the pieces need to be assembled. In my case, I have to assemble the interior dividers and mount them to the base before adding the edge pieces. Discovering this after having already glued on the edge pieces would be disastrous!
Step 6: Glue the Pieces Together
Firmly push the two pieces together until the joint is completely seated. Wipe up any excess glue that was forced out of the joint.
Repeat the process for the remaining pieces of the box. Ensure that the pieces are square to each other as you go since the first joints may dry before the box is completely assembled. Once the box is fully assembled, clamp the edges together to prevent the joints from pushing apart before they dry completely. If your box is fairly complex, it may be best to do the gluing in more than one session in order to properly clamp each joint. I glued the interior dividers to the bottom of my box and "clamped" it using a stack of books. After it had dried I went ahead and glued on the sides of the box.