Alzapiedi joins the Saints after three years with league rivals Concord Rangers as assistant-manager to Adam Flanagan.
Alzapiedi is a UEFA A licensed coach who has had spells at Ware, Harlow Town, Canvey Island and Cheshunt as manager.
Commenting on the news, Saints manager Ian Allinson told the club`s official website: “I have known Glen for a number of years and I know what a great coach he is. I wanted someone with experience at this level and he certainly has that, I’m really look forward to working with Glen over the summer and next season.”
Alzapiedi replaces Lee Allinson, who resigned as his father`s number two to take up the managerial role at Evo-Stik League South Premier side Biggleswade Town earlier this week.