Amy, you have done a thorough job on the weeds, number one priority.
Now I would indeed rake off the leaves, ideal for composting with any green leaves, coffee grounds, fresh manure etc. Remove/cut any slugs you see!
Then spread some compost, say 2in/5cm and by time of planting those flowers, slug numbers will be much less.
Stay vigilant with dusk patrols for the week or two after planting.
May your summer be flowery.
