I’ve having many issues trying to overlap a custom Rounded Container that has different widgets inside, in a Sliver App Bar. I’ve seen it was a very common problem a few years ago, but I couldn’t find anything that worked for me.

I’ve tried different ways to achieve it, with a Stack at the beginning, with a Stack in the flexibleSpace of the Sliver App Bar, with Persistant Header, but nothing worked.
What I need is very simple.
I have this (https://i.sstatic.net/jydnIRBF.png)
And what I need is to get the Rounded Container a few pixels over the image.
This is my code:

return Scaffold(
      backgroundColor: Theme.of(context).colorScheme.background,
      body: Stack(
        children: [
          CustomScrollView(
            slivers: [
              SliverAppBar(
                backgroundColor: Theme.of(context).colorScheme.background,
                stretch: true,
                onStretchTrigger: () async {},
                forceElevated: true,
                pinned: true,
                expandedHeight: SizeConfig.screenHeight * 0.3,
                flexibleSpace: FlexibleSpaceBar(
                  background: Stack(
                    children: [
                      Positioned(
                        top: 0,
                        left: 0,
                        right: 0,
                        bottom: 0,
                        child: Image.asset(
                          'assets/images/sign-up-bg.jpg',
                          fit: BoxFit.cover,
                        ),
                      ),
                      
                    ],
                  ),
                ),
              ),
              SliverList(
                delegate: SliverChildBuilderDelegate(
                  (context, index) => TopRoundedContainer(
                    size: EdgeInsets.only(
                      top: SizeConfig.screenHeight * 0.25,
                    ),
                    color: Theme.of(context).colorScheme.secondary,
                    padding: EdgeInsets.only(
                      top: SizeConfig.screenHeight * 0.04,
                    ),
                    child: Column(
                      children: [
                        CustomButton(
                          text: 'Edit Profile',
                          press: () {
                            Navigator.pushNamed(
                              context,
                              PhotographerEditProfile.routeName,
                            );
                          },
                          buttonColor: Theme.of(context).colorScheme.background,
                          textColor: Theme.of(context).colorScheme.surface,
                        ),
                      ],
                    ),
                  ),
                  childCount: 1,
                ),
              ),
            ],
          ),
        ],
      ),
    );