Botania doesn't help much with mob transport. You can use luminizers, but to put any items or mobs into a luminizer, it has to be moved onto a luminizer launcher first. For a Narslimmus setup it's probably easier if you just cover the spawn area of the slimes with the area of effect of the flowers in some way. Keep in mind that you don't need to place the collecting mana spreaders right next to the flowers, as they have a decent binding range.