The connector was made as a separate piece to improve the print quality of the joining area. Print the connector on its side, the base flat and the spike with the connector hole on the bottom. You can always glue the connector to one of the two other pieces if you prefer.
The model was made from the provided Base.stl so the fusion360 file doesn't have the change history prior to my changes. The connector parameters are adjustable to your liking.
The author remixed this model.
I split the Base.stl model into two pieces that can be re-connected with a connector.