The 23-year-old spent last season on loan at Boreham Wood and joins League Two Stevenage on a season-long loan.
Before departing, Ashby-Hammond penned a new one-year professional contract, with Fulham holding an option to extend by a further 12 months.
"I am really excited to get going", said Ashby-Hammond. "There's a good group of lads here, and my conversations with the manager have been positive. To get my first step into the football league is a challenge that I need to face, and I'm ready for it.
"I learnt and developed a lot as a player last season, and I'm looking forward to continuing that with Stevenage."
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