Pearity

At its simplest, you can define a direct conversion:

minecraft:oak_boat -> tfc:wood/boat/oak

With this rule, a vanilla oak boat can be crafted directly into its TerraFirmaCraft counterpart.

Need true interchangeability? Use a bidirectional rule:

minecraft:oak_boat <-> tfc:wood/boat/oak

Now the transformation works both ways. Neither item is privileged.

Where the mod truly opens up is pattern-based matching. Two wildcards are supported:

? : a match wildcard that captures variable parts of an ID

• : a broad wildcard that matches across namespaces or paths

For example:

minecraft:?_boat <-> tfc:wood/boat/?
This single rule links every vanilla boat variant (oak, birch, spruce, and more) to its corresponding TFC version. 
Think of it like "Match ids minecraft:something_boat with tfc:wood/boat/something"

Push it further:

:?_boat <-> tfc:wood/boat/?
Now any conventionally named boat from any mod (namespace) becomes interchangeable with its TFC equivalent. 
Notice how "" can be replaced with anything, but "?" have to match.

Keep in mind these are just examples. You can always match any two item IDs, creating progression-breaking recipes. For example, this:

minecraft:dirt -> minecraft:diamond
Self explanatory

or this:

minecraft:egg -> create:*
Now you can automate the entire create catalog by having a single chicken

or a slightly more sensible one like this:

minecraft:_sapling -> minecraft:_sapling
You can now technically begin with any sapling and grow any tree