I don't have sufficient insight into the operation of couriers operating in the EU. But I can tell you what I prefer to do. Instead of trying to hide the contraband in some decoy, which becomes immediately obvious under X-ray, I prefer to make the package look like a standard oder from an online shop. I just use a different label on the product and don't try to hide it. That way it raises no red flags when going through X-ray inspection which is how parcels are checked most of the time.
DHL probably operates drop-off lockers where you can leave your parcel to be collected, but they tend to have a video camera so it also carries some risk.