I've been making standard loaves shaped into boules. I've made them with white and wholemead flour. They taste good with a good rise. But, almost everytime I get these giant holes in the loaf (see photo). I've had flying crusts early on and it isn't this. I'm fairly sure it's to do with kneading.....do you guys agree? If it is, how do I resolve the problem? I've watched and watched many Youtube videos and tried my best to imitate their techniques. Is there something I'm missing?