Heat a small skillet over medium heat. When hot add the butter/coconut oil.
Add sliced avocado (the thickness just depends on your taste). Sprinkle with salt. Let cook on the first side until golden and crispy, about 5-7 minutes.
Flip and repeat with the other side. Add extra salt if necessary.
Don't waste the salty butter in the pan. Use it on bread or to cook some greens.