Darius Slay likes to add sound effects whenever his tackles are shown on film. He sits in the back left corner of the Eagles’ defensive backs meeting room, and, like a class clown, sends his teammates into laughter. Hey, smack ‘em! “It could be pitch quiet in there, 7 o’clock in the morning, and you can hear a pin drop, and he’s giving sound effects on every hit,” cornerback Zech McPhearson said. “It could be even a conventional tackle, but he can also put a guy on the ground.” Slay says he’s the best tackler on the Eagles. He’s joking. Sort of. With his always-present devilish grin, it’s some…