Have to admit I'd never heard of Ash-by-Sandwich before. Anyway there was a William Hammond christened in Ash in March 1814 to parents John and Elizabeth.
First name(s) William
Last name Hammond
Birth year -
Baptism year 1814
Baptism date 27 Mar 1814
Place Ash, St Nicholas
Father's first name(s) John
Mother's first name(s) Elizabeth
County Kent
Country England
Register year range 1813-1822
Archive reference ASH
Archive Canterbury Cathedral Archives
Record set Kent, Canterbury Archdeaconry Baptisms
I found a John Hammond marrying an Elizabeth Joyner in Ash in 1805 who are likely to be William's parents.
First name(s) John
Last name Hammond
Marriage year 1805
Marriage date 26 Jan 1805
Place Ash, St Nicholas
Spouse's first name(s) Elizabeth
Spouse's last name Joyner
Groom's parish Ash Sandwich
Bride's parish Ash Sandwich
County Kent
Country England
Register year range 1783-1812
Archive reference ASH
Page 90
Archive Canterbury Cathedral Archives
Record set Kent, Canterbury Archdeaconry Marriages
The records are behind the paywall on findmypast. There's no mention of "Garrett" however and it wasn't the maiden name of his mother so it doesn't seem that likely.