You're getting close! They key thing here is creating a template PPT that has a slide area that takes up the whole slide. While you're using a custom template, you can also get rid of the title slide and no extra slide will render.
See here for an example template that I use in the code below to generate what I believe you are looking for.
The easiest thing to do would be to download template-no-title.pptx and put it in the same directory as your Rmd file that you will be knitting. Then, the Rmd file will look something like this:
---
output:
powerpoint_presentation:
reference_doc: "template-no-title.pptx"
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(
echo = FALSE,
message = FALSE,
warning = FALSE,
dev = "svg",
fig.width = 12,
fig.height = 7
)
```
```{r}
library(patchwork)
library(tidyverse)
# prep frequency table
freqtable <- table(mpg$manufacturer)
df <- as.data.frame.table(freqtable)
theme_set(theme_classic())
# Plot
g <- ggplot(df, aes(Var1, Freq))
g <- g + geom_bar(stat="identity", width = 0.5, fill="tomato2") +
theme(axis.text.x = element_text(angle=65, vjust=0.6)) +
theme(axis.title.x = element_blank())
g+g+g+g
```
And this is the slide that is rendered: