Peel potatoes if desired. Shred potatoes using a box grater on the large holes or a food processor with shredding disc.
Place shredded potatoes in a large bowl and fill with cold water. Swish around with your hands to release starch. Drain and repeat 3 times until water stays pretty clear.
Transfer potatoes to a clean dish towel, wrap up, and squeeze firmly to remove as much water as possible. Spread on paper towels and pat dry again thoroughly.
Preheat Blackstone griddle to medium-high heat, 375-400 degrees. Let preheat for 10 minutes.
Add oil to preheated griddle and spread with spatula to coat an area about 12x18 inches. Oil should shimmer but not smoke.
Dump dried shredded potatoes onto oiled area. Spread into an even layer about 0.25 to 0.5 inch thick. Press down firmly with spatula to create contact with griddle surface.
Sprinkle salt, pepper, garlic powder, and paprika over the top. Let cook undisturbed for 5-7 minutes until bottom is deep golden brown and crispy.
Add butter in small pieces around the edges and let melt. Break hash brown sheet into 4-6 sections with spatula and flip each section. Press down again with spatula.
Cook for another 5-7 minutes until second side is equally crispy and golden.
In the last 1-2 minutes, break hash brown sections into smaller chunks and spread out a bit. Toss around a few times to get all sides crispy.
Scrape off onto a plate and serve immediately.