How would I go about making a Player customization system?

You can write your topic however you want, but you need to answer these questions:
What do you want to achieve? Keep it simple and clear!

I’d like some tips/tricks on how I could make a player customization system, with assets I put into the game. Players would not be able to use Id’s from catalog assets, but from those that I ut into the game
What solutions have you tried so far?
I looked for a few similar posts, but none of them really got to the point.

I would really appreciate any ideas/suggestions for how to make this as well

Please note
Upon spawning the player I teleport them to a “Spawn box” where they can customize their avatar/user settings etc.

I recommend you look at other games with character customization for some inspiration.