Most samples you find are a deck of screenshots and a headshot. A hiring manager does not read those. Here is the shape that works, in three examples. Copy the skeleton and refill it with your own work, and put your own numbers where the sentences ask for them.
Calendar. Problem: the executive had no protected thinking time and a week of recurring invites nobody had audited in a year. Approach: you pulled every recurring meeting, cut the ones with no decision in them, pushed one-on-ones into a fixed two-day window, and defended two mornings against everyone including the CEO. Result: name the block of focus time you created and the number of recurring hours you removed. Those two numbers are the entire case study, and almost nobody writes them down.
Travel. Problem: a multi-city trip with a visa dependency and a board meeting that could not move. Approach: you booked a routing with a fallback leg, pre-cleared the paperwork, and built a one-page itinerary the executive could read on a phone in a taxi. Result: say what happened when a flight was cancelled and the meeting still ran. A rescued trip is the most quotable thing an EA can put on a page.
Board and exec ops. Problem: the board pack arrived late every quarter and the last twelve hours were always a scramble. Approach: you worked backwards from the meeting date, set a per-contributor content deadline, and chased in one thread instead of six. Result: the pack landed on the same day each quarter, and you can name the day. Confidentiality is not a reason to skip this one; see the honest part below.
The bio sits above all three. Two paragraphs, first person. The first says who you support and at what level: how many executives, what seniority, which time zones, what board cadence. The second says how you operate when something breaks, because that is the part being hired. Read it back and ask whether a stranger could now describe your Monday to someone else. If they could not, it is still a list of adjectives.