Place chicken, wild rice, onions, celery, carrots and poultry seasoning in a crockpot. Cover and cook on low for 7 - 8 hours.

Remove chicken and shred. Return to crock pot.

In a medium saucepan, melt the butter over medium heat. Add the flour and whisk together. After one minute, slowly add the milk while whisking constantly to prevent clumping.

Add the butter mixture to the crockpot and stir to combine. Season with salt and pepper to taste.