We have ours at the highest point of our fields, as sheep like to run uphill for safety.
It is also in about the smallest one to minimise any running around.
It is positioned by a gate, so when we have completed a task on each sheep we can pop them through into the next field. This is because we don't always complete every task on one day, so we know who's done and who's not.
Our fields have connecting gates all the way round, so we can play a kind of musical sheep, to get the group we want into the catching field ie the one with the pens.
Our tups are in a separate area across the road, and they are caught in a pen which is set across a bottle neck in a tiny paddock at one end of their pasture.