To install macOS in VirtualBox on Windows 11, you need to follow the five-step procedure mentioned in this article to do it successfully.

Learn how you can easily install Windows 11 on your M1 or M2 Apple Mac using UTM or Parallels Desktop virtualization software.

OpenCore Legacy Patcher has a thorough walk-through that you can use to download the version of macOS you want to run, and explains how to install it on the device of your choosing.