"Dark L" is "L" at the end of the word or after a vowel sound. Example: ball, pull.
"Light L" is "L" at the beginning or before a vowel sound. Example: light, love.
There are 4 explanations of how to pronounce "dark L":
1st explanation: the tongue tip must contact the ridge right behind the upper teeth.
2nd explanation: before the tongue tip must contact the ridge right behind the upper teeth, you must curl the tongue and make sound like /r/ before make the /l/ as in the 1st explanation.
3rd explanation: just put the tongue between upper and lower teeth is enough to make the dark L
4th explanation: the tongue tip must contact the ridge right behind the upper teeth & the back of the tongue raises up (a British teacher teaches that).
see this vid: https://www.youtube.com/watch?v=pejo6YC_BnM and https://www.youtube.com/watch?v=U4En7vG1wV4 for more info
So what is the correct way to make the "dark L"?