Agree with Jester S1.
However if you really want to slow it down whatever amount it is, you can make slotted flaps (like fowler flaps without the backwards movement to keep it simple) taking up to 30% of the wing (or more if you use flaperon mixing because you will be flying so slow the ailerons are not enough to control bank).
Leading edge flaps or slats also give a great help, however they limit the max speed quite significantly. I think the slotted flaps will get you what you are looking for.

Fly safe, be safe.