That's why I asked how you came up with the words. If they're not on a default word list, you may be able to strike out enough of them.
I assume the padding of OP's 12 mnemonic recovery words with additional 38 words to get some grid of 50 words was meant as some sort of disguise or hiding in plain sight or puzzle (for whom?). Using 38 words that don't belong to the mnemonic wordlist doesn't make sense, as it would be trivial to separate the recovery words from the padding words.
I repeat myself: don't do such things without proper documentation. It's a trap or recipe for future desaster as we see it here in this topic.
Now I have found a self-made puzzle of one of my seeds. I have about 30-50 seedphrase words here, I have written them down in a pattern that I can't remember. Only with the right pattern can I put the words in the right order.
Now that we know the number is 50, OP states clearly for me, they are seedphrase words, i.e. are words from mnemonic wordlist. Or is my interpretation wrong?