Toe

Removal of m, replacement of i with o

Toes

Added an S

Toy
Dropped the s, changed e to y

Boy

Changed the Y to a B

If you change a letter, you have to drop another letter.... You can't just change one and leave it [yes]
Or you can add a letter instead. So it would be like:
Toys
Added an S

Joy

Dropped the S, changed the T to a J

Joys
Added an s

Boy

Removed the S and changed the J to a B.

So

Removed the y and changed the B to an S.

Sod

Added a D

Soda

Added an A

Sodas

Added an S

Coda

Removed the S and changed the other S to a C.

Boa

Removed the D and changed the C to a B.

Boat

Added a t

Boats

Added an S.

(I know it's taking the easy way, but I can't see any other option going anywhere. Blame it on the lazy this time.)

Bloats

Added an L

Bleat

Removed the S and changed the O to an E.

Bled

Removed the T and changed the A to a D

Bleed

Added an E

Lead

Removed the B, changed the second E to an A.

Lad - Removed O.

Laid

Added an I between A and D