I need some help with making my sideboard. I like slaughter games there, but the other two not too sure. what else can I include in the sideboard.

There is a couple of cards that people dont agree with here, like the flayer and the killing waves. however, I really like this cards and they actually work very very well in the deck. crypt ghast is a bit out of place I would admit. The only thing I will think he will be good for is the x spell. dont know what to add instead of him. I would like it to keep it standard (although is almost out of standard already)