Standoff Mount
A standoff engine mount is a mount where your engine is connected to a backplate that rests behind the engine, rather than a beam that rests underneath the engine to support it. The standoff mount can be tricky, depending on the design, but as long as you have a backplate that's strong enough to support the engine, it's a very strong design.
Standoff Supports
The key part of a standoff design are the standoff supports that link your engine to the backplate. There are no fewer than four supports on an engine that's meant to be mounted this way. The supports screw into the back plate, putting the engine firmly in front of where the driver would be, if the RC vehicle had one.
Materials
Standoff supports are made from a number of different materials. Commercial kits tend to favor aluminum supports because they're lightweight, but still strong enough to get the job done. Many RC pilots prefer to make their own standoff supports from wood dowels, though, because they're cheaper and easier to work with in a home shop. However, supports could also be made from steel or even heavy plastic.
Tools
All you need to install your standoff engine mounts is a drill (a drill press is recommended, but a hand drill will work if you're careful) and a wrench or socket if you're intending to use bolts or screws. Many RC hobbyists use glue instead, such as wood glue if the project they're working on is wooden.