|1.||flop a sack|
In an office setting, coffee generally comes in little "sacks" of grounds that are proportioned to fill one pot. When one person puts in one package of coffee, he is said to have flopped a sack. Therefore, making coffee at work is to "flop a sack."
I went to the kitchen area and there was no more coffee left in the pot; therefore, I decided to flop a sack.