Microwave spinach in large microwaveable bowl on HIGH 3 min. or just until wilted, stirring after 1-1/2 min. Cool slightly.
Meanwhile, beat cream cheese and flour in medium bowl with mixer until blended. Gradually add chicken broth, mixing well after each addition. Add pepper, nutmeg and 1 tsp. thyme; mix well.
Squeeze spinach dry. Place half the potatoes in slow cooker sprayed with cooking spray; cover with layers of spinach, and half each of the cream cheese mixture and Swiss cheese. Top with layers of remaining potatoes, cream cheese mixture and Swiss cheese; cover with lid.
Cook on HIGH 2-1/2 to 3 hours. Turn slow cooker off. Let potatoes stand 20 min.
Microwave bread crumbs in medium microwaveable bowl 1-1/2 min. or until lightly browned, stirring after 1 min. Sprinkle over potato mixture along with the remaining thyme.