Something I never understood, the SOUL is meant to be essentially the real you or in Flowey's own words the culmination of your being...how exactly does Flowey have Asriel's conscience and memories if he hasn't got a SOUL? The matters pertaining to the SOUL seem to be the weakest part of Toby's writing with all the inconsistencies but I suppose it's not too grievous a flaw.
Flowey has Asriel's essence. When a monster dies, their essence will live on in their dust. Asriel's dust spread across the garden, where the flowers bloomed. Alphys later used the first one that did for her experiments, and that's how Flowey was born.
Thought so, just wanted to cross check with another Undertale fan.