When they took a slice out of my infected lower leg last winter, it was just too wide to attempt closing. We just irrigated it with saline 3 times a day and bandaged it. I was taking oral antibiotics of course. the wound slowly graduated over and I did not need a skin graft. Under SHTF conditions, I would have used my raw wildflower & buckwheat honey. It has worked on smaller skin infections better than antibiotic ointments that they Doctor gave me.
In the ancient days, gashes were washed with herb infused oils and simply bound closed. It could drain if needed that way too.