- Assign ability scores as usual. Roll for it, use the array, point-buy, whatever it is you lot do at your table.
- You get to pick your race as usual.
- You get to pick your background, so you start with a couple skill proficiencies and some combination of tool proficiencies and languages.
- All of your equipment comes from your background.
- You start with 4 + Con mod hit points. When you acquire a class, just replace this with the class's starting hit points. (1)
- Your proficiency bonus is +1. It becomes +2 when you acquire a class.
- You have no saving throw, weapon, or armor proficiencies unless they came from your racial abilities.
- Gaining a class after one adventure, assuming your character survives, feels appropriate.
(1) - Maybe 6 + Con mod, if you're feeling generous.