Impress - Split color background

I’m trying to create a theme for LibreOffice Impress where the background is two colors split vertically. The left half should be one color and the right another.I tried to trick the gradient feature into doing this for me but it wouldn’t let me use below 3 increments. Any idea how I can do this without having to draw a filled box?

Click master view. Right click on the slide. Select Settings. In the “Page Setup” dialog box, choose Background and the Gradient button. Choose a gradient and/or configure the desired gradient.