There isn't necessarily a "best" way to configure a 12-tech slot explorer for maximum travel, but there are certainly ways to optimize it for better performance. Here are a few tips:
Make sure your tech slots are properly leveled and upgraded. This will ensure that your explorer can make the most of its available techs.
Alternatively, you can also focus on upgrading a specific tech slot (or two) that will be most useful for your travels. This approach will require more careful planning, but can ultimately save you time and resources.
Be sure to equip your explorer with the best gear available. This includes things like high-quality engines, chassis, and weapons.
Finally, try to keep your explorer's weight as low as possible. This will help it move faster and use less fuel.