Step 1: Print Templates I - Mask
Now if you have a cardboard printer, now is the time to use it (I wish I had one). For those without fancy awesomeness, just a regular black and white printer is all you need (or trace off a monitor, etc).
Print off the two images on this step. Ignore that the image is messy, it wont matter.
Next, tape the paper to a nice piece of cardboard. Grab an x-acto blade and trace cut your image onto a firm sheet of cardboard (good cardboard). Start be cutting the lines closest to the center, this will help you avoid ripping the paper latter, along with keep the paper taped in place properly.
Do this for both images. It doesn't matter if you use exactly the same type of cardboard.
Finally, you will need to make a cloned duplicate of the shape of each piece. So you will have two face pieces and two whatever-shaped pieces. HOWEVER, you only need to make one copy of each nice and pretty. The duplicate only needs to be a solid cutout to go behind the intricate image so you can paint a background.
Wait, not done yet-- you will need to make a somewhat complicated bend in the face mask piece(s), both of them. Make a cut through the cardboard (in the location commented in the picture) and then push the halves together to get the mask to bend as if to fit your faces bend a bit. You will have to do this for that piece's duplicate as well except the cut will be much larger to get the bend to work right (cut about half the mask down on that piece). Ask questions in the comments space if you have any...
Set these aside for now and continue to the next step...
Step 2: Print Templates II - Tentacles
If that confused you, just look at the final mask picture and then come back to here. It should make sense... eventually?
Step 3: Painting
You can choose whatever you want, just paint it now or forever love cardboard colors.
Let dry before continuing (duh)
Step 4: Affixation (Love for an Octopus)
Get a feel for where you want each tentacle by holding them on and then looking at the mask. Or you can recruit the help of a friend or clamps (they don't bite, ...softly...)
I used clamps and my own hands since I was trying to keep it secret. Once you think you know where everything goes, you can either mark it on the back with sharpie or pencil, or you can just eyeball it when you are gluing (my choice).
I love gorilla glue so I am going to assume that you should use it unless you are convicted by god to use something different.
So, lick your finger, wet application areas, apply glue lightly (you don't need much and you DON'T want it to ooze onto the front of the mask!), then clamp and let dry. I only had 2 clamps so I did this in 4 steps (2 at a time) total...
Hint: you can use paper to block the glue from oozing over the edges and onto the front of the mask if you are worried (which you should be because it is a pain to remove cleanly)
Once finished with the tentacles, grab that silly-shaped piece and lightly glue it onto the front of the mask as shown in the pictures.
Finally, glue on an elastic band to fit around your head and you are done!
Step 5: Octopus Invasion!
I would like to give credit for the idea to an artist's website where I first saw the image but I don't have the URL still, just the original pictures which are on this step (they are not my pictures). I'm sure a quick Google search of the artist's name (written on the images) would recover their website's URL, go for it.
They deserve much of the credit seeing as how I took my design directly from their work. I only can try to help other people enjoy this awesomeness!
I love their mask and I think I made a pretty comparably cool mask myself :) enjoy!