Here is where you can find to customize the naming of the flow run, the name of the flow is pulled from the function name if its not provided

Adding a little example from the release notes when this was introduced:

import pendulum
from prefect import task, flow

@task(task_run_name="{greeting}-{name}")
def my_task(name, greeting="hi"):
    print(f"{greeting} {name}!")

@flow(flow_run_name="{date:%A}-run")
def my_flow(date):
    return my_task(name="chris")

my_flow(date=pendulum.now())