Preheat oven to 400℉. Prepare a large baking pan with foil, if desired.
Wash and dry potatoes then place on the baking pan. Drizzle or spray potatoes with oil until lightly coated. Sprinkle potatoes lightly with salt, if desired.
Bake potatoes uncovered on baking pan for 1 hour, or until a fork can easily be inserted into the potatoes, or once the potatoes have reached an internal temperature of 200℉.
Once potatoes have baked, remove from the oven and allow to cool until you can safely handle them. Lower the oven temperature to 350℉.
Slice each potato in half lengthwise. Into a large bowl, gently scoop out the center of the potatoes leaving about ¼” rim of potato from the skin.
Gently mash the potatoes until broken up. Add the butter, sour cream, flaxseed, milk, salt, garlic powder, and pepper. Stir and mash to desired consistency.
Fold in the chopped bacon, grated cheese, and sliced green onion until combined.
Scoop the mixture back into the potato halves, dividing equally. Gently press the mixture into the halves and top with additional cheese and bacon, if desired.
Bake at 350℉ for about 15 minutes to warm potatoes and melt cheese. Top with fresh green onion or chives and serve warm.