I think he originally planned to reunite her with Romeo and then use their love to end the Montague-Capulet feud but when she saw Romeo dead and killed herself...well he couldn't really do anything with her then :L
Friar Lawerence's plan was for Romeo to take Juliet away to Mantua with him where they could live together.
His plan is to hide in the tomb with Juliet. That should have been his plan all along, and he should have got on it sooner.
in act 4 scene 1 Juliet arrives at Friar Lawrence's cell to find some kind of help to stop the marriage between her and Paris. Juliet threatens to kill herself if there is no solution to get to Romeo so Friar Lawerence explains his plan to create a potion where she will fall into a deep sleep and pretend to be dead. while eveyone thinks she's dead Romeo would come get her and run off with her and they would be together. Juliet accepts the potion and Friar lawerence begins to write the letter about the plan to Romeo and gives it to Friar John to give to Romeo. Balthazar(romeo servant) sees Juliets funeral and goes off to tell Romeo about it in ACT 5 scene 1 not knowing it was all fake. Balthazar makes it before friar john so Romeo doesnt get the letter about the plan and never finds out that Juliet was never actually dead.
Balthasar ruins the friar's plan by beating Friar John to delivering the message of Juliet's fake death. By telling Romeo before the Friar it caused Romeo to believe Juliet was actually dead.
Romeo wants the Friar to marry him to Juliet.
Friar Lawrence must send a message to Mantua to inform Romeo about Juliet's faked death plan. He wants Romeo to be aware of the situation so he can return to Verona and be with Juliet when she awakens. The message is crucial to ensure that the couple can reunite and avoid the tragic consequences of miscommunication. Without this message, Romeo may not understand Juliet's situation and could inadvertently lead to further tragedy.
Friar Laurence asks Friar John to deliver a letter to Romeo explaining the plan to fake Juliet's death.
Juliet and Friar Lawrence made the plan to fake Juliet's death so she could runaway with Romeo. They had planed for her to take a vile that would make her cold and fall asleep for 48 hours. Friar Lawrence sent a note to Romeo telling of their plan so Romeo and Friar Lawrence could go retrieve Juliet once her funeral was over.
Juliet threat to kill her self
Friar Laurence in Romeo and Juliet, appears to play a small role, because of his mere seven scenes. However, closer examination reveals that the Friar plays a fundamental role in the development of the story. He is a confidant to Romeo, moves the plot, and is instrumental to the tragedy at the end of the play. At the beginning of the play the reader learns that Friar Laurence and Romeo are close friends. After Romeo explains to the Friar his love for Juliet, he tells him that him and Juliet must marry to end the feud between the two families. Also, his plan to make Juliet sleep for 48 hours while Romeo comes and takes her away, failed. He is the reason behind Romeo and Juliets death. _NOUR SOLIMAN_
The friar and Juliet can control their actions and decisions within the plan, such as Juliet taking the potion and pretending to be dead. They can also control how they communicate with each other to ensure the plan is executed smoothly. However, they cannot control external factors or other people's actions that may impact the outcome of the plan.
She was anxious and desperate. If the Friar had not thought of a plan her intent was to kill herself, right there.