I used to pronunce "le" , like the one in "idle" wrongly , we simply pronunce it as "o" , but not long ago we were told it's wrong .
Since languages like Chinese and Brazilian Portuguese don't have a final L sound, speakers of these languages often don't pronounce it in English either.
One thing that may help you is instead of rounding your lips when you come to the end of the word, relax them. At the same time bring your tongue towards the top of the teeth and and let it rest there slightly.
I hope that helps.
American Accent Workshop