Code:
local b = CreateFrame("Button", "MyButton", UIParent, "UIPanelButtonTemplate")
b:SetSize(80 ,22) -- width, height
b:SetText("Button!")
b:SetPoint("CENTER")
b:SetScript("OnClick", function()
print("I'm in your buttonz")
end)
This gives you the most basic interface-button, like "Okay" and "Cancel" that you see in the interface options.