cssgrid

source("https://install-github.me/atusy/cssgrid")

library(cssgrid)
style <- "border: solid black;"
grid_layout(
  grid_item("A", area = "a", style = style),
  grid_item("B", area = "b", style = style),
  grid_item("C", area = "c", style = style),
  cols = c("1fr 2fr"), rows = c("1fr 1fr"), areas = c("a b", "a c"),
  style = style
)