Line a 6-quart slow cooker with a slow cooker liner (do not use an oven liner). Place the pie crust in the bottom of the lined slow cooker and gently press it into the bottom and slightly up the sides so it fits snugly. Avoid stretching the crust.
In a large mixing bowl, whisk together the eggs, corn syrup, brown sugar, melted butter, and vanilla extract until smooth and well combined.
Stir in the pecan halves until evenly coated.
Carefully pour the filling into the prepared pie crust, making sure not to overfill the crust.
Cover and cook on High for 3 hours, or until the filling is mostly set with just a slight jiggle in the center.
Turn off the slow cooker, remove the lid, and let the pie cool in the slow cooker for at least 1 hour. This allows the filling to fully set.
Carefully lift the pie out of the slow cooker using the liner. Transfer to a serving platter if desired.
Slice and serve, or refrigerate until ready to serve.
Notes
Don't skip the cooling time. The pie needs at least 1 hour to set before removing it from the slow cooker or it may fall apart.
Store leftover pie covered in the refrigerator for up to 5 days.
For the cleanest slices, chill the pie for 1-2 hours after it has cooled completely before serving.