1. Download and install .NET 7 SDK (https://dotnet.microsoft.com/download/dotnet/7.0)
2. Download and install Git CLI (https://git-scm.com/downloads)
3. Create a Github account (https://github.com/)
4. Prob restart your PC just in case, or don't
5. Open CMD
6. Execute the following commands, IN ORDER:

> git clone https://github.com/Ryujinx/Ryujinx.git Ryujinx
(it should probably ask you to login on Github at this point)
> git clone https://github.com/riperiperi/Ryujinx.git PR3830
> git clone https://github.com/gdkchan/Ryujinx.git PR3748
> cd PR3830
> git checkout perf/multi-region-volatile
> cd ../PR3748
> git checkout dei-hle
> cd ../Ryujinx
> git remote add PR3830 ../PR3830
> git remote add PR3748 ../PR3748
> git remote update
> git switch -c custom-build
> git merge --allow-unrelated-histories PR3830/perf/multi-region-volatile
> git merge --allow-unrelated-histories PR3748/dei-hle
> dotnet build -c Release -o build
> explorer build

If everything works out correctly, you should now be in your custom Ryujinx folder. Run Ryujinx.exe. Profit.