For the Crust:

Preheat oven to 400°F. Lightly grease the bottom and sides of a 9-inch pie plate with butter. Set aside.
In a food processor, pulse the oats and the pecans until roughly pulverized – you are looking for small pieces of pecans and some larger pieces of oats.
Place in a bowl with the flour, sugar, and salt. Add the butter and stir until thoroughly combined.
Press the mixture into the bottom and up the sides of the prepared pie plate. Bake for 12 minutes or until lightly browned. Remove from the oven and allow to cool while you prepare the filling.
For the Filling:

Wash, dry, and remove the tops from the strawberries. Place 1 ½ cups of the berries in a food processor and process until pureed.
In a medium saucepan, whisk together the strawberry puree, sugar, cornstarch, and water. Place the pan over medium heat, whisking frequently, and cook until the mixture becomes thick and bubbly. Remove from heat and whisk in the vanilla extract.
Set aside to cool for about 5 minutes, whisking occasionally.
While the filling is cooling, slice the remaining strawberries in half (small berries can be left whole if desired). Place a heaping ¼ cup of the puree mixture on the bottom of the pie crust, spreading with a spatula.
Arrange the halved berries in the pie plate on top of the puree, then pour the remaining puree mixture on top of the berries, covering them as evenly as possible.
Chill for at least 2 hours, or until ready to serve. Pie is best served the day it is cut to prevent the fresh berries from leaking their juices, but will still taste great up to three days later.