How to actually shadow Korean
A method, not a rule
Shadow the rhythm before the words.
Korean has flatter stress than English. Learners often import English stress and become hard to understand even with correct grammar. Hum the sentence first, then add words.
Work in one-breath chunks.
A sentence you cannot say in one breath is too long to shadow. Cut it at a particle boundary and repeat the half until it is automatic.
Repeat *after* the ending, not during.
Because the verb is last, starting to repeat early trains you to guess the wrong ending. Wait, then repeat the whole shape.
Ten sentences deeply beats a hundred once.
The goal of shadowing is a motor habit, not coverage. When a sentence comes out without thinking, move on.