Whisk 2 tsp. Diamond Crystal or 1¼ tsp. Morton kosher salt and 2 ½ cups warm water in a large bowl until salt dissolves, about 1 minute.

Slowly pour in 2 cups (326 g) precooked white cornmeal arepa flour, vigorously mixing by hand as you add the flour. It will start out thin and porridge-like and quickly become a soft, thick dough when all the flour is added. Continue kneading for about 2 minutes, ensuring no lumps remain (some small ones are okay). Dough should be moist and tacky but not sticky. (If it feels too sticky, add a tablespoon of flour at a time, mixing well after each addition. Shape a small ball of dough into a disk—if the edges crack, the dough is too dry. Add water a tablespoon at a time to adjust texture.) Cover bowl tightly with a lid or plastic wrap and set aside for at least 10 minutes and up to 2 hours to fully hydrate.

Divide dough into 8 portions (eyeballing is fine). Lightly grease your palms with vegetable oil. Flatten each dough ball into a disk about 4" across and approximately ⅓" thick. Transfer disks to a parchment-lined rimmed baking sheet. Cover tightly with plastic wrap to prevent dough from drying out as you cook arepas.

Position rack in center of oven; preheat to 200°. Heat a large nonstick or cast-iron skillet with lid over medium-high. Using a silicone pastry brush or crumpled paper towel, coat pan with ½ tsp. vegetable oil. Place arepas in pan 1–2 at a time (depending on how many fit), cover, and cook until underside is dry with golden brown spots, 7–9 minutes. Uncover, flip using an offset spatula, and continue to cook, uncovered, until second side is dry with pale golden spots, about 4 minutes. Arepa will sound faintly hollow when tapped. Transfer to a wire rack set over a rimmed baking sheet; transfer to oven to keep warm while you cook remaining arepas, lightly oiling skillet with remaining ½ tsp. vegetable oil between batches.

To serve: hold a warm arepa between a kitchen towel to protect your hand from escaping steam. Using a sharp paring knife, slit arepa around the edges (like a bagel) to create a pocket. Inside will be slightly doughy (if it bothers you, scrape off some of the dough with the paring knife) and tacky but not raw. Fill split area with butter, cheese, and/or avocado and serve warm.