Here's a simple, short circuit inspired by Mantorp park (
https://youtu.be/RRRJyrcT7uY)
2.2km anticlockwise, with a short oval (0.5km / 0.3miles) suitable for legends or similar.
There aren't any very tight corners, and the 800m back straight (~) should enable some good slipstream action.
Only 10 turns, its nice to simplify now and again...