The 27-year-old came through Fulham's academy and represented England at youth level before gaining experience on loan with Chipstead, Maidenhead United and Boreham Wood.
He starred in Boreham Wood's memorable FA Cup run, including a clean sheet against AFC Bournemouth, before helping Stevenage secure promotion to League One during a successful loan spell.
“It feels amazing, looking around here the facilities look amazing and all the guys here seem like great people so I’m delighted to be here at an ambitious club and I can’t wait to get started,” said Ashby-Hammond.
“The manager has told me it’s an ambitious club here and I’m very excited to be stepping into that and try as much as I can to help the team and I’m thankful that he’s (Dean) found that I’d be a good fit for his team so I’m looking forward to getting going.”