Less sticky rice and lentils

There is a couple of possible reasons I can think of.

Over stirring the mixture could be breaking the rice down releasing more of the starches which will be making the sauce thicker and sticking the rice into clumps.

Over cooked rice again making the rice overly sticky.

Like you've mentioned, lack of liquid. If the sauce is getting far too thick the starches will be more concentrated again sticking the grains together.

If the sauce is thick then certainly adding more water should help loosen it up a bit. Soaking the rice in cold water for half an hour before and then rinsing a few times will help get rid of some excess starch.

Also a possible factor is your choice of rice type. Some are more "sticky" than others.

Without tasting it myself it's hard to give a 100% reason but hopefully you will get a better result by paying attention to all the above.

If after all the above methods one last ditched effort might be as follow. 12 years ago when I was just starting out in my first kitchen I remember my head chef telling me "when you pour you're rice into boiling water, you must make sure they all fall freely and hit the water individually". Now I've remembered this ever since and thought about it every time I've cooked rice since, I've never done it though and can see NO reason why it would work or make any difference.

It's also worth noting I've never used a rice cooker in my life, not even sure what they are or do...

I have tried this myself. Although it depends on the type of rice that one gets (for example: the Japanese rice is the stickiest among them, because it is meant to be sticky, in order to make sushi rolls), but the following method has worked for me.

When you are cooking your rice in a pot, this would be easier, although it works with rice cooker too. But it is easier with a pot whose lid is usually clear while the lid of the rice cooker is almost never transparent.

Cooking the rice in a pot on a stove:

Once you see the water comes to a boil with rice in it, let it stay boil for about 10 seconds. Then quickly add cold water to it (enough to out out the boil).

And when it comes to a boil again, repeat the process. Repeat the process until you think the rice is fully cooked (or the way you want it), and quickly dump the hot water out and add cold water to it again and quickly drain it. The result is: the rice is cooked but they don't stick to each other. If you are making soup with the rice, add the cooked rice last after you shut off the flame for the soup.

This has worked well for me.

There are 2 things you can do to make things less sticky:

1. Rinse your rice and lentils at least twice (or under a tap for 30 seconds). Rice has a layer of loose starch on the outside which will make things sticky, rinsing will wash this starch off. Lentils will also be less sticky when washed beforehand
2. Add a small amount of oil or butter to the dry rice and lentils, then add your water. 1 tsp per cup (about 240ml) usually works for me, any more and it can get too oily