extreme care must be taken when things are done manually, specifically in this case because converting the entropy (coin flips) to mnemonic is done based on index of each word and the numbers beside each word on github is the line number.
in other words when you get 1 (00000000001) then your word is "ability" and NOT "abandon".
if the line numbers are used the end result will not be the same as what a BIP39 tool would generate from the same entropy and also you will be using a 2047 word long list instead of 2048 since you'll be deleting the last word (2048=zoo).