You're going to need an assistant for this one. Here's how to ruin dinner Method #19. Like the other methods, this is not an exact recipe, just a method. (see method: 36 17 42 29 88 81)
Here we go. I'm ruining chicken and chicken stock today. Slow cook your ingredients for at least several hours. You really want to be invested here. Then, set the finished items on the counter (in my case, the chicken and stock). Here's where an assistant is needed. You must be in the other room while dinner cools so you can work with it. your assistant must come up with an errand for you to run. Gather the kids, scoot everyone to the potty, gather jackets and shoes and head out the door. This will work best if you ask your assistant to go back to the kitchen to check that the stove is off. See, you've already forgotten that the meat is sitting out.
Now, go have some fun. Run 17 errands. Return home right at dinner time, all the while, feeling good that dinner is already mostly made... except wait... what did you do with dinner when you finished it.... wait, surely it's not still sitting out. Surely when you sent your assistant into the kitchen, they took care of it. No? Wait, meat sat on the counter all afternoon! congratulations, you have ruined dinner.