You can do it either way. They should do fine.

If you can reconsider the landscape fabric - I would. I garden for a living, and I can tell you from experience, that after a year or so, the landscape fabric will cause wayyyy more problems than it solves.

I want to second Carrie. Landscape fabric is okay for a low maintenance shrub planting with pre-emergents; it isn't really suitable for a perennial border.

Ryan

(Ryan! We meet again...)

The lily of the valley has thug tendencies and can probably outrun your landscaping fabric.

Each of the other plants you mention will sooner or eventually outgrow its slit.

If you dream of generous clumps of Hosta offset by those lovely ferny fronds of Dicentra - go for a reasonably thick cover of fine to medium nugget-size bark mulch over a generous helping of aged commercially made compost (to ensure no weed seeds).