HR Managers/ Bosses - how do you let someone go?

New boss here. I need to let someone go. We work remotely and I'm just not happy with their performance at all. They were on a probation period. How's the best way to do it, over a phone call? Zoom meeting? Formal email?

* Thank you all. Yes we have discussed their lack of performance but nothing is changing and unfortunately we can't rely on someone who does their own thing, does not listen to instruction and takes half a day to respond to their manager on things. We can't keep expressing how much more on the ball we expect him to be, he always apologises and says yes he's up for the task but his actions say otherwise.