You could do this, if you don’t care about security, by studying the relevant Bitcoin improvement proposal – BIP-39
You shouldn’t do this because your phrase will not be randomly chosen and will be weak and vulnerable.
There is no benefit to doing this because, despite the name “mnemonic phrase”, seed phrases are not intended to be memorised but are intended to reduce transcription errors. They should be written down or stamped in metal, not memorised.









