If you 'invert' a mesh by dragging one sides vertices to the other, it will be rendered inside-out, as if you are looking into an open box. That's how most people do skyboxes. There's a lot of useful info in this guide: https://www.notion.so/FAQ-Tricks-and-Workarounds-175da9c4b7ca4a92848fe26f798af5d... Inverting is at the top of the linked page.