In a large mixing bowl, combine the plain flour, sugar, salt, instant yeast, and baking soda, ensuring that the yeast does not come into direct contact with the salt. Stir together until well blended, about 1 minute.

Gradually pour in warm tap water while mixing with an electric beater on low speed for approximately 1 minute until you achieve a smooth, thick batter.

Cover the bowl with a clean kitchen towel and allow it to rest in a warm location for 30-45 minutes until the surface is frothy and bubbly.

Grease and dust the insides of your crumpet rings with a little oil and flour. Set them aside.

Preheat a non-stick skillet over medium-high heat for about 3-4 minutes.

Place the greased crumpet rings into the skillet and pour about 1/4 cup of batter into each ring. Cook for 5-6 minutes until edges dry out and bubbles rise.

Reduce heat to low-medium and cook for another 5-6 minutes until the tops are dry and bubbles pop.

Carefully remove the crumpet rings and flip each crumpet for 2-3 seconds to seal the tops slightly, then place on a wire rack to cool.

Toast the cooled crumpets in a toaster or under a broiler until golden brown, usually about 2-3 minutes.