In a small bowl, combine the warm water, sugar, and instant yeast. Allow it to sit for about 5-10 minutes until it becomes frothy.
In a large mixing bowl, whisk together the all-purpose flour and salt. Make a well in the center of the flour mixture.
Once the yeast mixture is frothy, add the egg and melted margarine to it. Mix well to combine.
Pour the wet mixture into the well of the dry ingredients. Stir with a wooden spoon or dough scraper until it begins to come together.
Transfer the dough to a lightly floured surface and knead for about 5-7 minutes until it is smooth and elastic. If the dough is too sticky, sprinkle a little more flour as needed.
Place the dough in a lightly greased bowl, cover it with a clean kitchen towel, and let it rise in a warm place for about 1 hour, or until it has doubled in size.
After the dough has risen, punch it down to release any air bubbles. Divide the dough into 12 equal pieces and shape them into small balls. Place them on a baking sheet lined with parchment paper, leaving some space between each bun.
Cover the shaped buns with the kitchen towel and allow them to rise for another 30 minutes until they are puffy.
While the buns are rising, preheat your oven to 350°F (175°C).
Once the buns have risen, brush the tops with melted butter for a beautiful golden finish. Bake them in the preheated oven for 15-20 minutes, or until they are golden brown.
Remove the buns from the oven and let them cool on a wire rack. Serve them warm or at room temperature with your favorite slider fillings!