你可以使用pandoc div（即:::::，或:::等）并为它们分配CSS类或id，然后在一个单独的style.css文件中为类或id选择器定义css规则。

显示演示文稿.Rmd

---
title: "Layout in RevealJs Presentation"
output: 
  revealjs::revealjs_presentation:
    css: style.css
---

## R Markdown

::::: {style="display: flex;"}

:::: {.column1}

::: {.section1}

**This is section 1**

Lorem ipsum dolor sit amet consectetur adipiscing elit, urna consequat felis vehicula class ultricies mollis dictumst, aenean non a in donec nulla.

:::

::: {.section2}

**This is section 2**

Lorem ipsum dolor sit amet consectetur adipiscing elit, urna consequat felis vehicula class ultricies mollis dictumst, aenean non a in donec nulla.

:::

::::

:::: {.column2}

::: {.section3}

**This is section 3**

```{r}
print("This is section 3")

:::

::: {.section4}

This is section 4

print("This is section 4")

:::

::::

:::::

**样式.css**

.column1,
.column2 {
width: 50%;
}

.section1 {
text-align: left;
color: blue;
margin: 10px 20px 0 0 !important;
font-size: 25px !important;
}

.section2 {
text-align: left;
color: red;
margin: 50px 20px 0 0 !important;
font-size: 25px !important;
}

.section3 {
margin: 10px 20px 0 0 !important;
background-color: dodgerblue;
font-size: 25px !important;
}

.section4 {
margin: 50px 20px 0 0 !important;
background-color: coral;
font-size: 25px !important;
}

.section3 pre,
.section4 pre {
background-color: white;
}

![](https://i.stack.imgur.com/GaNez.png)

作为参考，请阅读Rmarkdown Cookbook中的这一节。

您还可以定义div元素，如

<div id="NW"></div>
<div id="NE"></div>
<div id="SW"></div>
<div id="SE"></div>

然后分配您需要的CSS。
看一下here。