I work in the States and I'm thinking to go visit my friend in Canada. I have access to an Icon A5 and was thinking to fly from my closest lake in Vermont to his house which is also on a lake. What would be the protocols for doing this? Customs wise. Since I believe I would have to file a flight plan. How would immigration work since I am not planning to land at an airport and I'm also not a citizen of either the US or Canada?
Whenever you land in the US from a departure point not in the US, you have to land at an Airport of Entry as your first US destination airport. It does not have to be a big airport. There are plenty of Class D airports that qualify. You can verify which airports are AOEs in the US Chart Supplement. Some (big ones) are also marked as such on the sectionals.
When crossing the US border, you will need to have arranged customs clearance with the US CBP beforehand if you are landing at a small AOE. You may also need a US CBP DTOPS decal for your aircraft. Then, of course, there is the flight plan. Once you have cleared US CBP, you can fly to any other US domestic destination of your choice.
I would think that when flying into Canada, the TCCA would have similar rules.