In the first bowl, stir together flour and garlic salt. In the second bowl, beat eggs thoroughly with a fork. In the third bowl, add bread crumbs.
Cut Mozzarella block into 20-24 cheese sticks (just under 1/2” thick and about 3” long).
Dredge cheese stick in flour, tapping off the excess then dip in egg until coated. Let the excess drip back into the bowl then dip again in flour followed by egg.
Roll the cheese stick in bread crumbs, turning until all sides are well-coated then transfer to a platter, cover, and freeze for 45 minutes. Heat oil over medium heat to 350˚F on a thermometer. If you drop a pinch of crumbs into the oil, they should sizzle and bubble.
Once the oil is hot, add cheese sticks in small batches (4 at a time) and fry for 60-90 seconds, turning halfway and remove as soon as the outside is golden brown and crisp and there is any sign of cheese oozing out. Make sure the oil reheats to 350°F between batches. Transfer fried cheese sticks to a paper towel-lined plate to soak up any excess oil.