Heat canola oil in a pan over medium heat.
Cut the potato into thin, even slices, about 4-5 slices per sandwich. Add potato slices to the pan, cooking on both sides until browned and crispy. Transfer cooked potato slices to a plate and season with salt, pepper, and garlic powder.
In another pan, cook bacon on medium heat until fully cooked. Transfer cooked strips to a paper towel-lined plate to drain.
Meanwhile, butter one side of each slice of bread. On two of the slices, buttered side down, layer one slice of cheddar cheese and one tablespoon of sour cream.
Fan out the potato slices on the bottom slices of bread. Top each with another small dollop of sour cream, chopped green onion, two strips of bacon, and a second slice of cheese. Finish each sandwich with the remaining bread slices, buttered side up.
Grill sandwiches over medium heat until bread is golden brown and toasted on both sides, about 3-4 minutes. Enjoy!