John Gill Commentary Leviticus 5:12

"And he shall bring it to the priest, and the priest shall take his handful of it as the memorial thereof, and burn it on the altar, upon the offerings of Jehovah made by fire: it is a sin-offering." — Leviticus 5:12 (ASV)

Then shall he bring it to the priest
The flour just as it was, not kneaded and made into a cake, as appears by what follows:

and the priest shall take his handful of it ;
as much of the flour as he could hold in one hand:

[even] a memorial thereof ;
to bring to mind his sin, and the goodness of God in admitting of an offering for it, and forgiving it upon that:

and burn [it] on the altar, according to the offerings made by fire
unto the Lord ;
in the same manner as other burnt offerings were made:

it [is] a sin [offering] ;
or an expiatory sacrifice for sin.