Use Enum.chunk/2 to group elements into sub-lists, and Map.new/2 to convert it into a Map:
Enum.chunk/2
Map.new/2
[1, 2, 3, 4, 5, 6] |> Enum.chunk(2) |> Map.new(fn [k, v] -> {k, v} end)
Would give:
%{1 => 2, 3 => 4, 5 => 6}