Slice the strawberries (about 4-5 slices per berry), and place them in a small bowl. Sprinkle with 2 teaspoons granulated sugar, and stir the strawberries until they are coated in sugar. Let them rest in the bowl for 10-15 minutes, until some juice starts to accumulate in the bottom of the bowl.
Transfer the strawberries and any juices from the bowl directly into a cocktail shaker. Muddle until the strawberries are totally broken down and very juicy, about 30 seconds to a minute.
Pour the tequila, lime juice, triple sec, and orange juice into the shaker. Drizzle in the agave syrup and sprinkle in a pinch of sea salt (or kosher salt.) Fill the shaker halfway with ice.
Shake vigorously for 20-30 seconds until the shaker is super cold.
Strain the strawberry margaritas into two glasses full of crushed ice.* Garnish with a strawberry slice or lime wedge, and serve immediately.
Notes
*To make a rim for these margaritas, combine equal parts salt and sugar on a small plate. Run a lime wedge over the rims of the glasses, then dip the glasses into the salt and sugar mixture. Shake off any extra, then fill the glasses with crushed ice.