The safest way to thaw London broil steak is to place the steak in the refrigerator and allow it to thaw slowly. Yet, this can take hours; if you forgot to put the steak in the refrigerator in the morning, you won't have time to thaw your meat for dinner when you get home from work in the evening. Another option is using the microwave, following your microwave's manufacturer's thawing instructions. If you aren't careful, though, microwave thawing can cook the edges of your steak. There is a third safe thawing method.
Remove the London broil steak from its packaging.
Place the steak in a plastic food storage bag and seal it. When closing, remove as much air as possible. You want the bag airtight.
Set a large pan in the kitchen sink and fill it with cold water.
Submerge the steak in the water and place a plate or similar heavy object atop the steak, to keep the meat under the water. Replace the water with cold water every half hour. It will take less than an hour for a pound of meat to thaw.