Stansted Airport only has one single terminal for all flights, therefore it’s never necessary to switch between terminals.
There is also no airside transit facility – meaning if you are connecting between two flights at Stansted, you’ll need to follow everyone else through passport control and pick up any checked bags. Once you’ve arrived landside, you can then re-check any bags, pass through the security check, and back into the departure lounge.
As you’ll be passing the UK border, an ETA or transit visa may be required, depending on your nationality.
Given the possibility for delays, it’s ideal to have at least three hours between flights, although two hours would likely be fine if your inbound flight arrives on time.
If you have an overnight layover, you can find out which hotels are accessable from the terminal building here.
If you have a longer layover with time to head into London itself, see the Stansted to London guide.