Do something random.
Note first you have to think about what that means: asking “what?” or “what do you mean?” ruins the imperative. The mind then turns to a category of actions set down in advance or suggested unconsciously as “random”. You try your best to just let it happen without thinking about it, that is, to let the subconscious take over.
Now consider the times when you are part of a group that is trying to deliberately choose some course of action. The choice might come with a vote, or a few key concessions by objectors, or by a few people in the group just giving up. But there is almost always some amount of time when the writing is more or less on the wall, and when we become aware that the results have been set from some time ago.
Both are things that people call “free choice”. Both involve contributions from pre-conscious factors. The first has to turn to a pre-set category of “random” looking actions, and no doubt if we studies these we would find various social and subconscious influences. The second often involves the awareness that the writing is on the way, and that the plan has already been set before the definitive act that sets it.
But here’s the main point: anyone can concede the basic phenomenology of the act of choosing without seeing the subconscious or pre-set factors as doing away with the freedom of the choice. There will always be conditions on the act of deliberation, but to do away with choice altogether requires seeing even the deliberation as illusory.