I want to landscape the final area of my garden previously covered in bark
chippings.

Two years ago I felled two large Leylandii trees - the stumps, 18 inches in
diameter, remain. They are a few inches out of the ground and attempts to
kill them with crystals added between the trunk and bark do not appear to
have been successful.

I want to lawn the area and plant apple trees.

Will they survive/grow?

How can I remove the stumps? There is no room/access for one of those fancy
stump removers.

Any advice would be appreciated please?