The first step for a hardware attacker is to open up the device to look at the chips on the PCB and various exposed interfaces. This can be protected to an extent using uncommon screws, which are tough to open or by using things such as ultrasonic welding or high-temperature glue to seal the multiple hardware enclosures together.
Some of the common screw types are shown in the following figure:
If you decide to have unique/less common device screws, it would make it tougher for attackers to open up your device, and the only option in most cases would be to break it open. Force opening, and even normal opening, can be resisted by adding components, which sense and detect the opening of a device, which is discussed in the next section.