Well you lose alot of power, but certainly the easiest way is to run an inverter from the full charged battery and a battery charger from the inverter.
I did this a bit to start with when I rented a remote house I kept off grid while there, but had no charging source there.
In my truck was a battery bank, I charged it at my main home from the grid, wind gennies, while driving etc...
At the remote house was a bank also. It ran the lower power needs durring the day while no one was home. To keep it charged sometimes I would run an inverter from the battery bank in the truck, I think a 400watt inverter would run the charger at 20amps, and over night the house bank was getting a 20amp charge all night. When I needed more charging I ran the charger from a 5K inverter on the truck battery bank and charged at 40 amps. I did alot of things different ways different times, that was one of them.
Of course there was alot of loses involved running an inverter to make 120Vac just to run a charger to make 12Vdc again.
What and Why can be as important as how! Do you just need to keep a 2amp load running steady for a week some remote place and charge once a week? Then inverter and charger may work well and easy.