Prefs>Custom UI>Create New Menu.
Name it what you want, it will now show up on your menu bar.
Drag it from the menu bar to your left or right panel (this is just temporary).
Now that it's on your UI, you can ctrl+alt drag whatever buttons, sliders, materials, brushes, etc... you want into this menu.
You can also add sub-menus to it by going Prefs>Custom UI, and ctrl+alt drag the "Custom SubPalette" button into it. You can name the sub-palette by hold ctrl+alt and clicking on it once.
Once you have the stuff you want into it (you can always modify it more later), drag it off the side of your UI if you don't want it there (since you probably want to bind to a hotkey). And go to Prefs>Enable Customize, to turn off customization.
Now just hold ctrl+alt and click on your custom menu that's at the top and it will ask you to assign a hotkey. Done!
Afterwards, make sure to go Prefs>Config>Store Config.
As well as Prefs>Hotkeys>Store.