Lots of people here recommend eating Keto before an extended fast to make it easier but anything can be the ‘last meal’, more important to get started!
I eat until comfortably full and then start my clock
When I started my fast for the weekend I had: homemade tuna/sardine salad with 2 fresh bell peppers to dip in, 2 oranges, 2 servings of homemade chicken pot pie soup, crackers and a mug of hot cocoa. My typical eating window is anywhere between 1200-1400 or 1200-1600
Obviously not keto at all but the fact it was mostly in house/fresh really puts me on a good start. This last fast I felt the best I have in a while, finishing another 72hrs strong.