How to include cmake dependencies from source for static use - c++

Question

I'm currently writing an application which will make use of OpenCV and a few other dependencies using cmake. For the sake of the question only one dependency is relevant.
How can I construct a CmakeLists.txt file which downloads the OpenCV source from github and prepares it for static use within my application?
I have tried using ExternalProject_Add which looked promising until I realised the static libraries, etc are not available when they are needed (as far as i understand). I've had similar issues with FetchContent_Declare and related functions.
I understand I can build all my dependencies outside of the single CmakeLists.txt and use them with something like: find_package( OpenCV REQUIRED PATHS "${CMAKE_CURRENT_LIST_DIR}/../build/opencv" ). This works perfectly fine, however I'm hoping to have everything self contained within cmake so anyone that checks out my application wont have to do any special configuration or dependency fetching. Just cmake build and they would be ready to go.
Note:
I've tried many things and followed many blog posts over the past week to try and figure these things out. The post would be excruciatingly long if I were to document them all. At this point im very confused with how it should all work and im hoping someone can point out something obvious im missing.
I'm also aware i can use something like vcpkg instead of compiling these applications from source. Due to the dependencies not listed I am not going down this route.
Environment:
Windows 10
Visual Studio 2019
Cmake
CmakeLists.txt
cmake_minimum_required(VERSION 3.19)
# set the project name
project(test-depends)
set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
set(CMAKE_DEBUG_POSTFIX d)
# Global settings
set(GLOBAL_OUTPUT_PATH ${PROJECT_BINARY_DIR}/bin)
# dependencies
include(ExternalProject)
## other dependencies are here
# ......
## OpenCV contrib
ExternalProject_Add(opencv_contrib
GIT_REPOSITORY https://github.com/opencv/opencv_contrib.git
GIT_TAG 4.5.0
BUILD_COMMAND ""
CONFIGURE_COMMAND ""
INSTALL_COMMAND ""
)
ExternalProject_Get_Property(opencv_contrib SOURCE_DIR)
set(OPENCV_CONTRIB_SOURCE_DIR ${SOURCE_DIR})
# OpenCV
ExternalProject_Add(opencv
GIT_REPOSITORY https://github.com/opencv/opencv.git
GIT_TAG 4.5.0
DEPENDS opencv_contrib # other dependencies omitted
CMAKE_ARGS
-DCMAKE_INSTALL_PREFIX=${GLOBAL_OUTPUT_PATH}/opencv
-DBUILD_SHARED_LIBS=OFF
-DOPENCV_EXTRA_MODULES_PATH=${OPENCV_CONTRIB_SOURCE_DIR}/modules
-DINSTALL_CREATE_DISTRIB=ON
-DBUILD_EXAMPLES=OFF
-DWITH_CUDA=OFF
-DBUILD_DOCS=OFF
-DDENABLE_CXX11=ON
-DDBUILD_TESTS=OFF
-DBUILD_PERF_TESTS=OFF
)
ExternalProject_Get_Property(opencv SOURCE_DIR BINARY_DIR)
set(OPENCV_SOURCE_DIR ${SOURCE_DIR})
set(OPENCV_BINARY_DIR ${BINARY_DIR})
file(GLOB_RECURSE PROJECT_SOURCES "src/*.h" "src/*.cpp")
add_executable(${PROJECT_NAME} ${PROJECT_SOURCES})
set_property(TARGET ${PROJECT_NAME} PROPERTY CXX_STANDARD 20)
add_dependencies(${PROJECT_NAME} opencv)
include_directories(${GLOBAL_OUTPUT_PATH}/opencv/include)
target_link_directories( ${PROJECT_NAME}
PRIVATE ${OPENCV_BINARY_DIR}/lib
)
set(OpenCV_LIBS "ade;opencv_aruco450d;opencv_bgsegm450d;opencv_bioinspired450d;opencv_calib3d450d;opencv_ccalib450d;opencv_core450d;opencv_datasets450d;opencv_dnn450d;opencv_dnn_objdetect450d;opencv_dnn_superres450d;opencv_dpm450d;opencv_face450d;opencv_features2d450d;opencv_flann450d;opencv_fuzzy450d;opencv_gapi450d;opencv_hfs450d;opencv_highgui450d;opencv_imgcodecs450d;opencv_imgproc450d;opencv_img_hash450d;opencv_intensity_transform450d;opencv_line_descriptor450d;opencv_mcc450d;opencv_ml450d;opencv_objdetect450d;opencv_optflow450d;opencv_phase_unwrapping450d;opencv_photo450d;opencv_plot450d;opencv_quality450d;opencv_rapid450d;opencv_reg450d;opencv_rgbd450d;opencv_saliency450d;opencv_shape450d;opencv_stereo450d;opencv_stitching450d;opencv_structured_light450d;opencv_superres450d;opencv_surface_matching450d;opencv_text450d;opencv_tracking450d;opencv_video450d;opencv_videoio450d;opencv_videostab450d;opencv_xfeatures2d450d;opencv_ximgproc450d;opencv_xobjdetect450d;opencv_xphoto450d;")
target_link_libraries(
${PROJECT_NAME}
PRIVATE "${OpenCV_LIBS}"
)
src/main.cpp
#include <iostream>
#include "opencv2/opencv.hpp"
void main() {
cv::Mat testing;
std::cout << "hello" << std::endl;
}