(note: although it might look like that the legs and stand are not the correct size, they actually are, all Jamie Oliver ovens have one size stand and legs)
It is the best to put the legs in to the stand by first placing the stand on the floor and putting in one leg. Then (best done with two people) pull back the second leg until it does fit in to the stand. This might take some force.
This has been designed like this so the legs will not seperate from the stand again after assembling.