Par-boil whole potatoes in salted water until barely tender (about 10 minutes), then drain and cool in cold water. Once cool, peel and cut into ½-inch pieces.
Combine the cut potatoes with diced bell peppers and onions in a bowl. Drizzle with oil and stir to coat. Add seasonings if desired.
Spread the mixture in a single layer on a parchment-lined baking sheet and freeze until solid (at least 4 hours).
Transfer the frozen mixture to freezer bags, remove excess air, seal, and label. Store in the freezer for up to 4 months.
Cook the frozen mixture in a nonstick skillet with oil over medium-high heat until crispy and golden brown, about 12 minutes, stirring occasionally. Alternatively, use an air fryer for a crispy result.