insert vs slip in

insert is a noun but slip in is not a noun.

Word	Noun	Adjective	Verb	Adverb
insert	Yes	No	Yes	No
slip in	No	No	Yes	No

As verbs, insert and slip in are synonyms defined as:

Other synonyms of insert include sneak in, stick in.

insert (noun)	slip in (noun)
(film) a still picture that is introduced and that interrupts the action of a film
(broadcasting) a local announcement inserted into a network program
an artifact that is inserted or is to be inserted
a folded section placed between the leaves of another publication

insert (verb)	slip in (verb)
place, fit, or thrust (something) into another thing	insert casually
insert casually
put or introduce into something
fit snugly into