Make the sauce: In a saucepan, combine quartered strawberries, brown sugar and lemon juice. Cut the vanilla pod lengthwise and scrub the seeds, adding both the pod and the seeds to the pot. Bring to a boil over medium-high heat, stirring occasionally. Lower the heat and place a couple tablespoons strawberry juice in a small bowl. Add flour and mix well. Add the strawberry juice-flour mixture to the sauce and stir well. Cook for about 8-10 minutes, stirring occasionally, until thickened and reduced in volume. Discard the vanilla pod once the sauce is ready. Refrigerate in a sealed container for one week.