Right now FlatArray has two factory method constructors: empty and apply.
One of these (empty) has a broken signature:
empty[Boxed, Unboxed](elems: Boxed*)(implicit boxings: BoxingConversions[Boxed, Unboxed], elemManifest: ClassManifest[Unboxed]): FlatArray[Boxed]
The "elems" provided are ignored, so they should be omitted.
Also, this array lacks a method of specifying a size (without elements) like .ofDim. It should be possible to allocate a FlatArray of a certain size without actually providing all the members.