Fastest way to grill four steaks three at a time

A grill has room for at most $3$ steaks at once and cooks only the side facing down. Each side of a steak needs $2$ minutes, and a steak is ready only when both of its sides are done. What is the shortest total time, in minutes, needed to finish $4$ steaks?

6 minutes. There are $8$ sides to cook and at most $3$ fit per $2$-minute slot, so at least $3$ slots are needed. Rotate so the grill is never under-used: sides $A_1,B_1,C_1$; then $A_2,B_2,D_1$; then $C_2,D_2$.