This puzzled me as well, so I did some digging. Turns out the sound is similar to the "LL" in Spanish, and the "y" sound in the English "yellow". So taglia (and other "gli" words) would be pronounced like TAHL-yah, with just a hint of an "L" sound. I am by no means an expert, nor a native speaker, but I tried to find native speakers saying words with the "gli" sound, so take this with a grain of salt. I hope this helps!