This pair of sounds are not linked quite as obviously as the pairs we have studied so far - but the movement of the tongue that is needed to make each sound is very similar. These sounds are “L” and “R”.
To make the “L” sound, the tip of your tongue brushes over the alveolar ridge like this:
L L L L L
In the warm up video one of the exercises uses the “L” sound to help isolate the tongue from the jaw to create a more open sound.