Am I no longer able to create a board without a team?

[Aaron Bell]

There used to be an option to create a private board. Where'd it go?

[Michael Pryor]

You can still create a private board but it will be part of a team/workspace. 

https://help.trello.com/article/1241-why-cant-i-create-a-board-outside-of-a-team-anymore

[Vero Rivas]

Hi @Aaron Bell 

  Create a team where the only member is you and assign that team to the new board, in this way you will have the problem solved.

Regards