How to create a convincing musical structure?

My question is how to create a piece that flows well? Even if you use a template like sonata form, the piece might not flow well, and i have a problem with this, maybe its due to me making stuff up on the spot. Does anyone have any advice?

There is no ''wikihow'' answer to this question...
It is a quest that composers are following their whole life.

For structure, there are so many parameters that it could help you to organise/list them and analyse pieces that you like for their form.

Perhaps the most difficult issue about form is that it can be perceived differently according to the person listening.