Cut poster board to size you are trying to make. Preferably not bigger than the pan you're going to be using. This can be a big size like I did for a sign, or smaller, regular sized papers.
Crumble it to get the desired look. Personally, I rolled it up and squeezed it around a bit and then flattened it out again.
Place the poster board into a rimmed sheet pan and pour the coffee into it. Enough so that it covers the poster board. Be sure to have some coffee left over in the cup. I'll explain in a later step.
Let sit for about 2 hours, flipping halfway and making sure poster board remains covered with coffee.
After 2 hours, turn your oven on to the lowest setting it can go.
Drain the coffee. It doesn't have to be completely dry, just get most of the coffee out of the pan.
Please, do NOT drink the coffee you're draining.
INSTEAD, fix yourself the remaining coffee you have left over. You're welcome.
With the sheet pan drained, take your instant coffee and sprinkle it around the edges of the poster board. After letting it sit for 2 minutes, take a napkin, and blot the excess of the instant coffee off. Do the same for the other side.
Take the poster board out of the sheet pan and dry the pan with paper towels. I used those same paper towels to line the sheet pan.
Place the poster board on the paper towels and put the pan in the oven to dry it out. Flip it every 3 or 4 minutes. You want to keep it in the oven till it's dry, roughly about 10 minutes, depending on numerous factors.
Once it's out, congratulations, you just made your own parchment!
When it feels like a normal temperature, go ahead and stick whatever vinyl lettering you have. Or you can also write on it if you have good handwriting unlike me.