There are two 'l sound' formations--also known as allophones of the 'l sound': a 'light l' and a 'velar' (or dark) 'l'. The 'velar l' is represented by the International Phonetic Alphabet symbol /ɫ/.
The following is a description for the light l; hereafter simply referred to as the 'l sound' /l/.
To create the /l/, the tip of the tongue is placed against the middle of the tooth ridge. The sound is created when air travels alongside the tip of the tongue, between the front of the tongue and the side teeth.