local id = elements.allocate("MYMOD", "NAME")
elements.element(id, elements.element(elements.DEFAULT_PT_WATR))

elements.property(id, "Name", "My Element")
elements.property(id, "Color", 0xFFFFFF)
elements.property(id, "MenuSection", elem.SC_LIQUID)

elements.property(id, "Update", function(i, x, y)
-- behavior here
end)

Full solid block 

elem = elements.allocate("MYMOD", "BLOCK")
elements.element(elem, elements.element(elements.DEFAULT_PT_WOOD))
elements.property(elem, "Name", "BLOCK")
elements.property(elem, "Description", "A custom block I made")
elements.property(elem, "Color", 0x00A0FF)
elements.property(elem, "MenuSection", elem.SC_SOLIDS)