для ячейки коллекшн вью я вот так делала
self.layer.masksToBounds = false
let shadowLayer = CAShapeLayer()
let radius = self.frame.height / 2
shadowLayer.path = UIBezierPath(roundedRect: self.bounds, byRoundingCorners: [.topLeft,.bottomLeft], cornerRadii: CGSize(width: radius, height: radius)).cgPath
shadowLayer.fillColor = UIColor.white.cgColor
shadowLayer.shadowColor = UIColor.lightGray.cgColor
shadowLayer.shadowPath = shadowLayer.path
shadowLayer.shadowOffset = CGSize(width: 2.0, height: 2.0)
shadowLayer.shadowOpacity = 2.0
shadowLayer.shadowRadius = 2.0
layer.insertSublayer(shadowLayer, at: 0)