The Google Now Launcher is probably the best way to get the stock and contemporary Android look as Google itself sees it. With the latest update to a beta version of the app aimed at developers, the Google Now Launcher makes it possible to use your phone in landscape mode (which we find awesome). Keep in mind that this update targets Android 6.0 Marshmallow and later devices, so you will not be able to install it on 5.x phones.
An interesting question in itself is: why does the problem with different sized icons exist in the first place? The reason lies in third-party Android app developers that often don't follow the guidelines for icon sizes that Google provides, cheating their way to attention (usually) by picking larger icon sizes. Having the icon size normalization feature would definitely be useful in this regard.
So how do you get hold of this current Google Now Launcher beta? The version is not published on the Google Play Store, but you can easily sideload on your Android device. Make sure to only use trusted websites when sideloading Android APKs to avoid malware.