Complex sentence: Pouring the beer into the glass requires skill as a lot of foam is built when pouring and without the right technique, you will invariably end up with a glass filled with a tiny bit of beer at the bottom and lots of foam on the top.
Split into simpler sentences: Pouring the beer into the glass requires skill as a lot of foam is built when pouring. Without the right technique, you will invariably end up with a glass filled with a tiny bit of beer at the bottom and lots of foam on the top.