Warning: This collar is designed to give an animal more freedom than an E-collar and therefore cannot be used in every situation that an E-collar is used. In particular, it may not prevent an animal from licking/biting its front paws or the end of its tail. However, with cats (and some short faced dogs) it will prevent the animal from using its front paws to scratch its face. In any case, you should always watch your pet for a while to make sure this collar works as intended.
Step 1: Materials
For large dogs you may want to fill the inside of the foam with cloth or smaller diameter foam so the dog can't simply crush the collar.
2. Electric or other plastic tape. The kind of tape you use is important as the collar is inevitably going to have contact with whatever your pet eats and drinks. I tried cloth athletic tape first and within a couple of days I had to negotiate terms with the colonies of bacteria that had seized control of the collar.
3. Shoelace, or other thick piece of string.
Step 2: Measure and Cut the Foam
To calculate the length of foam you need the O.D. of the whole collar. The first step is to determine the diameter of your pet's neck. If your vet gave you an E-collar, you can use this to estimate the diameter, otherwise wrap your fingers around your pet's neck and guesstimate the diameter (Note: fur doesn't count). Again, overestimating is better than underestimating. The O.D. of the collar is attained by adding the diameter of your pet's neck to twice the O.D. of the insulation (e.g O.D. of foam = 5cm, diameter of neck = 6cm. 6+2*5=16. So the outside diameter of the whole collar will be 16cm.). The length of insulation will be the O.D. of the whole collar * Pi (e.g. 16cm * 3.14 = 50.24cm).
Step 3: Shaping the Insulation
The first picture is much clearer than the description so look at that before you read on. First, draw a straight line down the insulation. Then draw another line 90 degrees (1/4 of the circle) from the first. The material to be removed will be equilateral triangles with a base that is the radius, r (i.e. 1/2 the diameter) of the O.D. of the insulation. To do this, use a ruler to place a mark every r centimeters along one of the lines. Do the same for the other line, except shifting each mark by 1/2 r (i.e. 1/4 the O.D.). Then connect the dots to make triangles.
When you are done marking the triangles, cut them out (second picture).
Finally, test that it bends properly (third picture).
Step 4: Add String and Test
Step 5: Tape It Up
After the collar is taped poke a couple of small holes along the outside near each end (see picture). Then pass the string through these holes. This allows you to tighten the collar a little more than if you left the string in the center of the insulation.
You can wipe the collar once a day with a little rubbing alcohol to keep it clean.