Looks like she used a mold. Temper chocolate, make truffle shell in square mold, let set, fill with ganache, seal bottom with more chocolate. Just like for making bon bons or other candies with fillings.
pour amount of ganach into a lined pan, let set. top with another flavor, let set. finish with a third flavor, let set.
you may also like to use metal candy "bars" to keep the uniform hight.
when cool and firm, use a guitar or wire or knife to cut truffle into squares. enrobe with tempered couveture and set.
or before cutting you can "ice" the top of the block of truffle with tempered couveture then cut to squares so the layering is shown off. enjoy!:lips: