Hey! So one big area is the bat that you mentioned at the end, it’s very difficult to get a lot of spin with this type of bat of course.
A few things that will help your serve however in the meantime. Try to keep the top of the bat flat so that the tip does not drop down lower at the end, if this does happen you will end up with more sidespin rather than backspin.
Also really try to bring the wrist back as you throw the ball up, this will allow you to really brush under the ball and accelerate through the contact which will again help the spin you can get.
Also I think you can get your lower arm to come back more and hinge from the elbow as you bring the wrist through, this will help you be stable in the serves and get the same action consistently.
Let me know if you have any more questions 🙂
