The simplest method is to take an edge as a common edge and directly intercept it to make an congruent triangle. For example, take BC as the common side, intercept the length of AC, make an arc with B as the center, then intercept the length of AB, make an arc with C as the center, and intersect at one point to connect them.

A little more trouble than the first one. The parallelogram method is to do parallel lines first and then intercept them, and the rest is similar to the first one.

Find any point outside the triangle ABC, make three corresponding parallel lines and cut.