Obviously this year has been an anomaly, however on average employees are asked to be in the office for 6 days in a fortnight (with the remainder spent working from home). All supervisors I've had have been happy to let me self manage my flex time.
The agency takes a flexible approach - you can start work early or finish late, as long as you communicate this with your manager/supervisor and as long as you get the work done.
Agency is relatively flexible, so long as the work is done. I have a lot of flexibility choosing what hours of the day I'm doing my work, so long as I'm contactable by my supervisor/available to meetings.