In most situations I prefer to not use key pairs with EC2 instances. I just want to use my own SSH keys. Thus, most of the time I opt out of specifying or creating a key pair in the last step of launching an instance. Instead, I use cloud-init to install my keys when the instance is created. This isn’t groundbreaking, but I have to look up the syntax each time I do it. Hopefully putting it here will save me time in the future.
When spinning up an instance, the following goes into the user data text box in “Advanced Details” of the instance details step.