He first took up rugby when his father took him to Kent side Cranbrook RFC. Sloan was offered a trial at Harlequins. He impressed and was added to their academy, later on joining the senior side.[2]
Sloan represented both London Scottish and Ealing Trailfinders as part of his development as a young player at Harlequins. During these spells he was dual registered and still eligible for selection at Harlequins.[4]
Sloan made his Aviva Premiership debut in March 2014 after coming through Quins' academy. He signed a new contract with Harlequins on 11 January 2016 for an undisclosed length.[5]