Well, look at AiĆ½ota, the only way for that to be feasibly possible is if that region is extremely wet, the continent is entirely flat, and if it is a shield in a tectonic plate. Tutono is more possible because there could be a colliding plate (oddly curvy though) down the middle of it with another plate, however, other islands would have to exist. It also probably used to be two continents that merged together into one.
Continental shape, unless it is multiple plates like Asia, start with a triangle (or 2:3 rectangle), cutting pieces out of the triangle instead of adding them. For example, if you look at Africa, you can surround it with a triangle:
blah blah blah i got distracted by forum errors and imgur errors and imgur in general i will add more post tomorrow