Wash, hull, and coarsely chop strawberries in a large glass, ceramic, or stainless steel bowl. Mash with a potato masher to a fine texture, 1 or 2 minutes. Add sugar, lemon juice, and vanilla bean paste. Stir well and let stand until berries have released some of their juice, about 30 minutes. Add pectin, 1 tablespoon at a time, stirring until well combined after each addition. Let stand 5 minutes to activate pectin.
Spoon jam into clean, wide-mouth, half-pint jars, leaving 1/2-inch headspace. Wipe rims clean with a damp paper towel. Loosely apply clean lids and set jars in freezer. Freeze completely, about 5 hours.
Tighten lids. Store in freezer up to 1 year or in fridge up to 1 month.