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In a large bowl, pour 8 ounces of glue. Add 1 cup of water. Then add enough food coloring to create the shade of color that you want your flarp to be. Stir the ingredients until they’re evenly mixed. Either pour one cup of very warm water from a hot tap into a second bowl, or heat cold water until it’s simmering before you mix it with the borax. Then add 1.5 teaspoons of borax. Stir until the borax has totally dissolved.  Use a second, clean spoon to mix the borax, or wash the first spoon to remove any glue. For thicker, sturdier flare, add more borax, a half-teaspoon at a time. Pour the borax solution into the bowl with the glue mixture. Stir constantly for two minutes or more, until the consistency is even. Continue to stir if the coloring or texture still seems uneven. Line a surface area with parchment paper for easy clean-up. Once the mixture is cool enough to handle, remove it from the bowl. Massage and squeeze the flarp on the paper until its texture is consistently smooth and stretchy. Let it rest for ten minutes or so, and then start playing with it!

Summary:
Mix glue, water, and coloring together. Mix warm water and borax separately. Combine the two mixtures. Knead the mixture.