Mirroring texture inside GUI.Button

Hello. I don't actually know how to do that. Tried using GL.Matrix before drawing the element. That worked, however: 1. Button is not working even it is seen 2. Text, attached to a button is also mirrored

So the question is, how can I change a texture? Is there a way to, for example, attach texture to another variable, flip it there and then use it for a GUILayout?

I've tried doing:

 Texture2D texture = new Texture2D(-buttonSkin.box.normal.background.width, buttonSkin.box.normal.backgroun.heigh);
 
 button2Skin.box.normal.background = texture;

However it's not as easy as flipping GUI.DrawTexture();

Any suggestions?