Pieces of clay need to be joined with slip.
The way I was shown is: Add water to some of the clay to make a mix the consistency of milk or thin cream - that is called 'slip'. Roughen the surfaces that are to be joined with something like a toothbrush then apply slip to the roughened areas before pressing the pieces together (sliding them back and forth a little as you press them together also helps the bonding) then let the join dry out.
Even with really good joining the joins will be weaker than solid pieces and your design has a lot of joins Paddles

Does that sound right potters????