What is the possessive form of blocked when used as a verb. For example:
Remove the friend I blocked’s material.
Write, "Remove the material of the friend I blocked."
There is a stylistic problem, as the reader needs to recognize instantly that you are using 'friend-I-blocked' as a phrase. It's not strictly comparable to 'Queen of England', where there is a noun at the beginning and end of the phrase and where the phrase is in any case well established.