Instead of decanting you can filter it , just do it crudely first and then with paper like stuff , decanting is easier but you should put a clear solution into the freezer particles are a no-no
with extract filter residue i guess he means put the pieces you sifted out , solids left over after decanting in fresh water and repeat process , or you could just read it as repeat process
now the 2 thing is important , the whole principle of this tek is that , the ice cristals wil entrap impurities (like plant sugars and fats/ big molecules) and the alkaloids will get pushed out in front of the ice and will accumulate in the 1/3 (ideally) of solution that stays liquid , so your not only removing impurities , this is actually a better way than boiling down for reducing your solution (no loss) .
now the only way alkaloids will get trapped is when you disturb the ice , or the bottle is like dirty , particles in it , the ice will form pockets and entrap your solution and alkaloids , if all goess wel you wil have a layer of ice , like growing from the top in a horizontal bar with water underneath (should draw this sure it doesn't make much sense) so when you unscrew the cap and let the solution drain the ice will stay in the bottle.
if all went well the ice should be white ,1 save it however and repeat the process once.
oh and it's recommend to use more than 1 bottle at the time , don't fill your bottle more than half and you need a standard pet bottle like the normal bottles coke comes in , decent size and small neck , and plastic.
now the guy only does it 2 , i had to do it 3-4 times to get good smokeable quality stuff , guess it depends on a lot of factors. I'll be glad to help you with any other questions or if some of my explanations are unintelligible please point it out.