Place water and sugar into a small saucepan and bring to a boil over medium-high heat (stir frequently to dissolve the sugar and ensure it doesn't burn).
Once boiling, remove pan from heat and mix in 3 tablespoons of tapioca starch. Stir until fully incorporated.
Place the pan back on the heat and continuously stir until the mixture forms a gel-like consistency. Try to get it all mixed, but don’t worry if you still see small little chunks of starch at this point.
Turn off the heat, add the rest of the tapioca starch to the pan, and fold in to incorporate. It may seem too dry at first, but keep folding in – it’ll continue to incorporate. If it doesn't, add a teaspoon of water. If it's too wet, add a teaspoon of starch. It will look a bit shaggy at this point, which is normal (see photo for reference).
Carefully remove the dough from the pan and transfer it to a countertop or large cutting board. Knead the dough with your hands until it fully comes together (handle carefully, it should be hot, but not too hot to touch).
Divide the dough into 8 portions. Set one aside and wrap the remaining 7 in plastic wrap for now, to keep them from drying out.
Lightly flour your workspace with tapioca starch and begin rolling the one portion of dough you took out into a long strand, about 1/4 inch thick.
Working rather quickly, cut the strand into small, pea-sized pieces, then roll each piece into a ball using the tips of your fingers and palm of your hand. Set the rolled balls aside for now. Tip: keep a small bowl of water next to you, and cover half of the strand with plastic wrap while you’re rolling the other half, to prevent the pieces from drying out. If they begin to dry or crack, lightly wet your fingers with water and continue rolling. If they stick to your hands, dab them in tapioca starch and finish rolling.
Continue with the second portion of dough, making sure to leave the rest of the dough wrapped in plastic to prevent it from drying out. Roll into a strand, cut into pea-sized pieces, then roll each piece into a ball. Continue with the other 6 portions until all of the dough is formed. Tip: lightly wet the palms of your hands before rolling the dough into strands.
Sprinkle tapioca starch over the balls and gently roll them around to coat them in the starch.
Leave them out to dry for 4-6 hours, the timing mainly depends on the humidity levels in your home. Note: if you want to use some now, you don't need to wait for them to dry.
Transfer any unused, uncooked dried boba pearls to a freezer-safe bag, and freeze for up to 3 months. If you'd like to store them longer, vacuum seal them and freeze for 6+ months. Do not pre-cook them before storing, because they won't store well.