Using Wire Crimps, 453 U-Shaped
You can find Terminal Tab Cold Insert Connectors for sale all over the internet.
These are made from brass and are quite reasonably priced, about 2 to 3 cents each in volume.
You can easily connect two wires as described in the images below.
The connection is strong and does not need soldering.
Note, using glue lined heat shrink makes your connection moisture proof.
If your connector can accommodate stacking the wire strands, follow the instructions given.
If your connector is small, you may not be able to stack the strands as shown.
FYI
