For me it would be where the sun is shining, the house is tidy and there’s no chores to do.
Start off with a decent breakfast and a decent mug of coffee. I’d have had my run the previous day so can rest a bit. Maybe head out for a walk, grab some lunch at the local garden centre. I’ve just redownloaded the game Ingress after not playing it for years, so maybe play that for a couple of hours.
Get home and watch the F1 while I prepare and cook a lasagne in the afternoon. Smash said lasagne with a glass or two of a nice red wine and then spend the evening playing Minecraft for a few hours, then an hour or two of reading before bed.
The reality though is far different as I have two young kids!
But by that time most of your Sunday is gone, wouldn’t it be better going into the day that you still have two full days off?