Tickets for the ferry, operated by Somarco, from Puerto Ingeniero Ibañez to Chile Chico may be purchased at the docks or online here.
There is a fantastic waiting area at the dock in Puerto Ingeniero Ibañez with wifi, bathrooms, and a small café. Before you arrive at Puerto Ingeniero Ibañez, check the ferry schedule. Although Somarco has a fairly reliable schedule, it is possible the ferry may not run every day. It takes a little over two hours to cross the lake.
Town: Chile Chico
Chile Chico is slightly larger than Puerto Ingeniero Ibañez and has more housing and food options. It also has a larger grocery store and is the better resupply option.
Note: The picture above of Lago General Carrera is part of the public domain and was taken by Jorge Morales Piderit.