How to Make It
Spread butter evenly over cut sides of baguette halves. Spread jam evenly over cut sides of top baguette halves. Arrange turkey slices evenly over cut sides of bottom baguette halves. Top with cheese slices, drizzle with vinegar, and top with arugula. Replace top baguette halves. (You will have 2 assembled baguette sandwiches.)
Wrap each sandwich tightly with plastic wrap; place on a platter or baking sheet. Top each sandwich with a heavy skillet or baking sheet weighed down with cans. Place in refrigerator; chill at least 6 hours or overnight.
Remove plastic wrap from sandwiches. Cut each pressed sandwich crosswise into thirds (about 4-inch-long pieces).