I have several decent sized heads in my garden. The only way we really eat it is in vegetable soup. Could I slice about 1 inch thick slabs, wash it thoroughly, freeze it on a sheet for a couple hours then vacuum seal it for the deep freezer? If this won't work, what will?
Any help is appreciated.

wash it , cut into the size you use in the soup

blanch it in boiling water , then freeze it on the sheet tray and vacuum seal


or I could go on like Bubba about the many ways to use cabbage.

I think I eat a pound or more a week often.

Make sauerkraut out of it

All brassicas blanch and freeze well. Cabbage, turnips, collards can be proccessed that way. They also can well by raw pack and pressure can though may get to soft vs freeze.

The best option is to make a little sauerkraut.

It will last a very long time.

Wife and I make about 35/45 pounds every year in the Fall.

We enjoy all year long.

I make saurkraut as many above do. I pressure can mine after I ferment it for 4-6 weeks. I make about 6-9 quarts per year. I have never froze cabbage but that sounds like an option. I make many salads each year using cabbage as my main ingredient. The nice thing about cabbage as you can put a couple heads in a cool place and it will last a long time. Much longer than other greens I have worked with. I can see the blanched and frozen as a part of winter soups.

Bryce

Make friends with local Koreans and have them show you how to make kimchi. Good stuff! Traditional Koreans make hundreds of pounds of it. It’ll put hair on your chest until you get used to it!

If you have a lot, the easiest way is to pull it root and all and hang in a cellar...

Whatever you do, do not mix kimchi with german hefe weisse bier. Especially over a long weekend right up until Monday's 5am PT formation.

I love me some kimchi but that stuff needs to be handled carefully, lol. It's actually good for your gut despite what it does on the way out.