Step 1: Upload and Tweek
Note: If you use the web app on your Mac, the app doesn't work through Safari.
Open the App and Browse Community. You'll see a search box. Type in skull. There'll be a couple different kinds of skulls, but for this Instructable, we'll be using the one on the right with a tag of "scary skull" (see picture).
Open that version. Choose stacked slices for the construction technique. Then, change the slice direction if needed. We made it so the cuts were more diagonal rather than horizontal. Change the manufacturing settings to the size of your laser printer. Finally, change the size of the object. This is completely up to you.
Once you've tweaked the original design, click get plans. Export using PDF.
Note: Even if you don't have access to a laser printer, you can do it by hand. All you'd have to do is print out the images on a normal printer, cut out the stencil, pin it to cardboard, cut, and glue.
Note: Autodesk 123D is partnered with various 3D printing services. Check out this link for more information!
Step 2: Laser Cut
Put your piece of cardboard in the laser printer. Make sure it's down flat! Close the top and press "enter" when you're ready. Let it run. Ours took about 15 minutes. When it's done, open the top and take the pieces out.
Some pieces may not fall out like in the picture. You'll need to pop them out.
Step 3: Organize Pieces
Step 4: Start Glueing
When you're done glueing, you'll have a 3D skull sitting in front of you. We putt the gel glue in the eye sockets to give it a glazed look.