I have been helping a friend organize her home lately. We did her big chest freezer yesterday. It took us about 90 minutes because it was big. We put like items together so she would know how much of each thing she had. She can easily check now to see if she needs something before going grocery shopping again.
We used the basic method:
Pull everything out.
Organize it into like items.
Choose the items you want to keep.
Discard the rest.
Her freezer looks good now and she knows exactly what she has in it.
Sometimes going through stuff is overwhelming. It can be easier to declutter when you have someone with you. They can help keep you on task or help to share ideas or just help you plow through.