I formed two sizes of eyeballs in case I didn't like the really large one (I later ate the smaller one and it was delicious).
Roll out a thin circle of gum paste to cover the eyeball:
Cover the eyeball- you may need to make small triangle cuts in the excess so when you fold the gum paste on the bottom of the eyeball, it doesn't bunch too much.
Mix green food coloring into the white gum paste for the eyelid. I like to mix it with my hand in a plastic glove or even in a Ziploc bag so the coloring doesn't stay on my hands.
Roll it thin like a half moon using the eyeball as a measuring guide.
Color some gum paste blue and roll thin for the iris. I used a sprinkle container lid as a cutter:
Adhere the iris to the eyeball by brushing a little water on the backside of the blue circle and pressing it to the eyeball. Mix some black gum paste and roll thin for the pupil. I used a smaller sprinkle container lid for the pupil. Adhere the pupil by brushing a little water on the backside of the black pupil and place on top of the iris. Highlight the eye with a flatted ball of white gum paste and adhere to the pupil.
Now it is time to apply the eyelid to the eyeball. Brush the backside with water:
Press to the eyeball and trim the excess.
Ready to place on the cake. Right about then, my nephew Facetimed me and asked if I was making him a motorcycle cake. "A motorcycle cake?! You said a monster truck cake. Actually, I'm working on your cake right now and it is a monster truck cake but the cake is a monster eating a truck. What do you think about that?" He said good. I told him I'd text him a photo later.
Now the truck. I didn't take as many photos of the truck making process. It was getting late and I tend to keep working rather than pausing to grab the camera. First, I took the extra black gum paste and flattened it in my hand to make the mouth. The triangles I cut from the bottom of the eyeball so it wouldn't gather and bunch were used for the monster's teeth. Next, I colored some gum paste red for the tongue.
I had left-over green gum paste from the eyelid, so I formed a flattened ball for the rim of the wheel and made indentations with a pointed tool. A white band of gumpaste trimmed the rim and a small flattened ball was placed in the center for extra detail and then I sprayed the whole rim with silver Color Mist food color spray.
Allow the food color spray to dry. Then, roll a long black piece of gum paste and do an almost touching V pattern with a pointed tool for the tire tread. Add the black to the outside of the rim.
After the cookie was trimmed, I rolled orange gum paste and covered the cookie pieces.
There was enough gum paste to make a number 5. I eyeballed it and used the sprinkle lid for the cutout in the center. The last thing I did was add a furry rim above the eye with the green frosting to look like an eyebrow. It's subtle but game the cake even more dimension.
As far as specialty cakes go, this was a pretty simple one- taking only a couple of hours.
And that, my friends, made my day.