If I’m doing really sloppy things, I’ll put them in a container in the deep freeze overnight, and then pop them out, put into the bag, and vacuum pack.
But we’ve never had a problem with fresh meats or fish. One of our first experiences was with a whole salmon we got a Costco; husband cut it into steaks, vacuumed a few to a bag, and they kept well in the freezer for many months.
Diana from Wisconsin told me awhile back about doing fresh whole fish. I love whole rainbow trout on the grill but Costco only has a 4 or 5 pack. I got one and foodsaver froze the individual fish. They come out of the bag looking just as fresh.