Per Frame BoxColliders?

Hey there, I'm working a 2.5D beat em up style game using 2D sprites with a 3D environment and I'm working on finding an easier way to do per Frame hitboxes for attacks. The previous method I had followed a tutorial where I would have to put each frame into the scene and create a variable in the hitbox manager for each frame and store it in a hitbox manager. This method eats up data and I was curious if there was any easier way to go about adding per frame hit boxes. This is the method I had previously used and as stated "isn't the prettiest method." I guess I'm just having difficulties brainstorming an easier way to do this.

Thanks for any and all Input