Here is an actual photo, taken yesterday, how to do it. My Laser (in her blue covers) already stays at the wall. Her other friends soon did follow as one is able to see, so, she is not alone, during the winter
I live in upstate NY, and hang my boat from open rafters. Here's how.
I got two cheap block and tackles from harbor freight, and two six foot lifting slings, which I looped together. They are the purple ones. I also had an eight footer from a friend - yellow/tan in foto.
My roof trusses run front to back, and are open (no drywall) to below. I took two standard 2x4s and placed them up on top of the trusses, going side to side across the garage. I also attached the two Harbor Freight block and tackles to the roof beams above the trusses. I use the b&t to lift the boat up, loop one end of the lifting sling, onto one end of the two by. Once the boat is high enough, I slip the other end loop of the sling onto the other end of the 2 by. Then I lower the boat onto the slings. Boat runs front to back, 2 by and lifting slings run side to side. The 2-by spans 6 of the trusses, spreading the load. What I have that most don't is open access to the area above the roof trusses. Plus I have an extra high garage ceiling. Kinda dark and crowded up there.
FYI: I was warned by a dealer (and expert boat repairer) that storing a Laser upside down in the North (freezing weather) leads to problems. Moisture always seems to get in from leaks, condensation or gremlins and this moisture settles into the material under the deck, freezes, and delaminates the deck from the reinforcement material (a.k.a. "soft decks"). And as we know, repair is expense or impossible. He strongly suggests that hanging the boat by the gunwales is the safest way to store your Laser in freezing temperatures.
Hiker makes a good point, which is why you need an inspection port so that the inside can dry out. During the late season here in Maine we can have extended periods with very warm days and very cool (40° F) nights. This makes for some serious condensation inside the boats.
I have experienced situations where the inside of the boat has been perfectly dry and then the boat sits for 10 days (not being sailed) under the conditions described above and found a puddle of water in the trough just forward of the bottom of the mast tube. I have three ports (out of necessity - repairs) and would not recommend installing that many if you can avoid it. But it does allow me to monitor these things.