take the piece of antler that you are going to use for handle and boil it until center is soft, then use a flattened antler tine or rib bone,or even a flint drill and drillinto the center of the antler ...should be nice and soft now...
cut off as much antler you need to ensure good fit and a longer tang...
then press the blade down into the the antler handle while it is still rather soft...
then wait till dry.
this will be a SUPER STRONG FIT, but then you can fancy it up with some pitch glue and sinew and should be just fine.
thats one abo way.
mbg