That's my first instructable, but not my first costume!

This year my son wanted to be a french fries box for Halloween. French fries? Why not!

Step 1: Planning and Shopping

The planning was very ad-hoc: some internet research to see how other have done this before, some sketches on the black board, then let's go!

What we bought:

a foam seat-cushion: about 5cm thick, we found it at a fabric store for 13$
a can of yellow spray paint (4$)
cardboard: red for the exterior (1$), white for inside the fries box (0.50$)

We also used:

bungie cord (as shoulder straps. Use what you have, plain rope will do)
rugged cardboard box (for the box structure)

Tools:

sharp box cutter
transparent packing tape
double-face tape
ruler and tape

Step 2: Cutting the Fries

The seat cushion we used was just the right size for an oversized fry: we only needed to cut it on the length to get realistic looking giant potatoes sticks.

We marked the foam with a brown sharpie, thinking the line will make a nice "cooked" look on the edges. It does look nice, except I haven't done my math before starting. The cushion was not a multiple of the thick side, so my last lines were either to large or too thin. I decided to make thicker, non-square fries on the end, but doing that some lines are showing a bit too much on the middle of these fries. They are not that visible, but be cautious of your lines before tracing your fries!

The foam was relatively easy to cut with a sharp blade: make sure to use a fresh blade, long enough to cut in one shot through the cushion! I've put an old scrap wood board under the blade to cut without fear of damaging the material.

The resulting fries already looked like a stack of potatoes sticks, ready for deep fry!

Step 3: Test the Fit

At first I thought that the stack was a bit small for what I had in mind, so I tied them as-is around my son with a bungie cord, and well, that looked good enough just like that!

Step 4: Add Colors

We used a cheap spay paint we've bought for 4$ at the dollar store and gave a quick coat on the fries.

They were easy to paint: the color sticked well and just a small dose is enough.

Don't forget to paint the ends, and don't worry to stack them and turn them while you paint, they will not stick or loose their paint since the foam is absorbing everything right away. They should be dry to the touch very quickly ; we let them dry overnight to be on the safe side.

Step 5: Box Structure, Fries and Straps

For the box, we cutted two big 'T' out of a big carboard box we kept from a delivery. I cutted the size to fit my son shoulders width, so use your model for correct measurements here!

We then folded, stapled and taped together the two T to form a box, with empty holes on the side for the arms (sorry, forgot to take pictures of this step). Finally, we sticked white cardboard with transparent packing tape on the insides to hide the ugly brown cardboard (at the end you'll see that the fries are actually hiding this, so you could consider this an optional step).

To hold the box, I made little loops with some wire I had lying around. You could use anything strong enough here: electric wire, rope, etc. The other non-loopy side of the wire is taped to the other side for strength and to protect the finish.

Finally, we made notches on the other side and use a bungie-cord as straps; after setting the fries in place and adjusting the length to my son size I used tape to hold everything in place. I used again a bungie cord to hold the fries while fitting them nicely then just use packing tape to hold them permanently in place.

Step 6: Cover

For the cover, we cutted to size a piece of red cardboard (the type you would use for posters at the science faire).

I did not want to have shinny spot covered with tapes and other spots dull from the plain cardboard so I used double-faced tape to stick the paper cover on the cardboard structure.