rules not as yet tested for swiftly converting FLAILSNAILS PCs to DCC games and/or using OSR-compatible homebrew classes in DCC.
First, determine your character's base class:
If you fight good and do very little else, you are a Fighter.
If you fight good but also have some extra abilities such as ranger, paladin or racial powers, you are a Variant Fighter.
If you fight fairly well but have other abilities that make up at least 50% of your schtick, you are a Cleric.
If you have skills, sneaky stuff or other utilities that aren't fighting or magic, you are a Thief.
If casting spells is your primary thing, you are a Wizard.
Characters get attack bonus, action dice, critical tables and saving throws as per their base class.
Fighters get the Deed Die and Mighty Deed of Arms.
Variant Fighters don't get the Deed Die, and instead get an attack bonus equal to the average of the Deed Die they would have gotten, rounded down. (e.g. d3 = +1; d4 = +2; etc) They cannot perform Mighty Deeds of Arms.
Clerics and Wizards still cast spells as per their original system; no rolling on tables for you.
Thieves use whatever skills they had from their original system, but gain the ability to burn and regain Luck as a Thief.
Your DCC Strength, Agility, Stamina and Personality correspond to their equivalent stats in the original system. (Why they insisted on renaming Dex, Con and Cha I will never understand.) Your DCC Intelligence is the higher of your OSR Intelligence or Wisdom. Your Luck is rolled as you enter the DCC universe.