A Destiny Knot passes 5IVs between the parents
Breeding is just a matter of luck and RNG being kind to you. It is indeed very possible to get a 5IV Froakie but its not 100% garaunteed.
>Destiny Knot gives a combo of both the parents IV's. So you could get perfect IV's or non-perfect IV's unless you bred both parents to have perfect IV's.
For example : If neither parents did not have an IV in Sp.D then the offspring's IV inSp.D would be randomly generated.
2 flawless parents will not be guaranteed to give 5IVS
6IV parents 19.2708% of the time or 1 out of every 5.1892 eggs will produce 5IV Pokemon with a DK