Place the pork leg in a pot, ensuring a snug fit.
Add salt, peppercorn, garlic, onions, and bay leaves. Bring to a boil over high heat.
Once boiling, cover the pot and reduce the heat to low. Simmer for 1 hour or until the meat and skin are tender. Add water if needed to prevent drying.
Remove the pork leg, draining excess liquids. Place it on a rack over a pan to let liquids drip. Allow it to rest for 30 minutes.
Brush the skin with lye water and refrigerate uncovered for at least 5 hours or overnight.
Brush the skin with vinegar, rub salt, and rest for an additional 30 minutes. Use a kitchen or paper towel to remove excess salt.
Heat oil in a large, deep pot over medium-high heat. Gently add the pork leg, cover the pot, and wait until splattering sounds subside. Use a splatter screen if available.
Fry the pork leg until the skin is crispy, turning as needed. This takes about 30 minutes.
While waiting, combine the ingredients for the dipping sauce in a bowl and adjust it to your preferences.
Transfer to a plate with paper towels to drain excess oil. Serve warm with vinegar-soy sauce dip.