Maybe you’ve heard French, spoken some, and never noticed a difference between English ‘l’s and French ones. Well, there is a difference and if you can say it the French way, you’ll sound less like an English-speaker.
Say the word “fell.” Say it again and pay attention to where the sound is made. When you prounounce this kind of ‘l’ in English, can you feel the ‘l’ sound partially made in the back of your tongue/throat? It finishes with your tongue closing on the part behind your teeth, but the ‘l’ sound itself is at the back of your throat. The French ‘l’ is never like this. It’s made somewhat like how you would say the ‘l’ in the word ‘fly’. Say ‘fly’ now. Can you feel your tongue right behind your teeth? Now go back and forth between ‘fly’ and ‘fell’. Really feel the difference of how they are said. In French, you always want the ‘l’ with the tongue behind your teeth and it’ll stay in front.