If you are "self taught" you might also be inclined to be a rider who mostly rides alone. You can do modified intervals by mixing up your ride. Suppose you do weekend rides by yourself and go out 40 miles or so. Use a route that you are familiar with and has some flat portions without traffic lights.

During those rides, go for a burst of speed, first a normal pace and then begin to accelerate and reach a speed and hold that speed for a period of time. Then slow down and let your heart rate ease down.

Then repeat. Not only is this a physical challenge, but interval work plays on your mind as well. Your mind will tell you to quit after a few repeats. This is where mental toughness gets developed.

You actually should have a coach, otherwise you miss out on a lot of objectivity. My first encounter with intervals was in distance running for competition. I thought the coach was crazy when we had to do 20 repeats of quarter miles. After the 3rd repeat, I started to dread the next 17.