How to add actor to another actor in plugin development? Unreal engine 5.1.1

Hi,
My problem is that I want to design a custom cube actor in c++ since it has own properties.
Similarly, each face of the cube has its own properties, as well. To solution for this, I created a SubCubeActor class and a SidePanelActor. SubCubeActor has six different reference (FrontPanel, BackPanel, UpPanel, DownPanel, RightPanel, LeftPanel) in its class definition. I want to add SidePanels to this class but I couldnt do it.
My codes are:

include “Cube/SubPartCube.h”
include “Engine/EngineTypes.h”

ASubPartCube::ASubPartCube()
{
// Set this actor to call Tick() every frame. You can turn this off to improve performance if you don’t need it.
PrimaryActorTick.bCanEverTick = false;
SceneRootComponent = CreateDefaultSubobject(TEXT(“test_root”));
RootComponent = SceneRootComponent;

CreateSidePanelInstances();
AttachSidePanelsToRoot();

}

// Called when the game starts or when spawned
void ASubPartCube::BeginPlay()
{
Super::BeginPlay();
}

// Called every frame
void ASubPartCube::Tick(float DeltaTime)
{
Super::Tick(DeltaTime);
}

void ASubPartCube::AttachSidePanelsToRoot()
{
FrontFace->AttachToComponent(RootComponent, FAttachmentTransformRules::KeepRelativeTransform);
}

void ASubPartCube::CreateSidePanelInstances()
{
FrontFace = CreateDefaultSubobject(TEXT(“FrontFace”));

BackFace = CreateDefaultSubobject<ASidePanel>(TEXT("BackFace"));

}

include “Cube/SidePanel.h”
include “Engine/StaticMesh.h”
include “Components/StaticMeshComponent.h”
include “UObject/ConstructorHelpers.h”

ASidePanel::ASidePanel()
{
PrimaryActorTick.bCanEverTick = false;
static ConstructorHelpers::FObjectFinder MainMeshAsset(TEXT(“/Game/StarterContent/Shapes/Shape_Plane.Shape_Plane”));

if (MainMeshAsset.Succeeded()) {
	UStaticMeshComponent* FaceMesh = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("FaceMesh"));
	FaceMesh->SetStaticMesh(MainMeshAsset.Object);
	RootComponent = FaceMesh;
} 

}

// Called when the game starts or when spawned
void ASidePanel::BeginPlay()
{
Super::BeginPlay();
}

// Called every frame
void ASidePanel::Tick(float DeltaTime)
{
Super::Tick(DeltaTime);
}

I am not sure these method is the correct method right now since I am newbie in C++.