Hi. No, that isn't correct. Remember that the conditional perfect in spanish is formed with the conditional tense of the verb haber + a verb in the past participle form. So, the correct sentence is: Hubiera preferido la hora de la mañana para mis clases de español. If you are talking about a specific hour, you can also say: Hubiera preferido en la hora de la mañana mis clases de español. As an extra, your question isn't correct neither. You have to use the verb to be to form the complete meaning, so you can ask: ¿esta frase es correcta? Remember that the word "frase" is feminine, so the adjectif has to be in feminine too. I hope this could be helpful.

Hubiera preferido la hora de la mañana para mis clases de español

Hubiera/Hubiese preferido la hora de la mañana para mis clases de español