How to post data to firestore avoiding non-existent documents?

I have a data structure similar to this that I want to post to firestore database via REST API:

I manually created the House1 document, then Floor1 and Ground.

Ground contains the data:

REST API in R

Now, I am trying to use the firestore REST API in R to create the same thing.

library(httr)
library(jsonlite)

# POST function
post_data_to_firestore <- function(path, data, auth_token) {
  r <- httr::POST(
    url = sprintf("https://firestore.googleapis.com/v1beta1/%s", path),
    config = httr::add_headers(
      "Content-Type" = "application/json",
      "Authorization" = paste("Bearer", auth_token)
    ),
    body = data
  )
  return(r)
}

PROJECT_NAME <- "firebase-project"
COLLECTION <- "Block"
accessTokenu <- "access-token"

endpoint <- paste0("projects/", PROJECT_NAME, "/databases/(default)/documents/", COLLECTION)

data_list <- toJSON(
    list(
    fields = list(
      Name = list("stringValue" = "Ground")
    )
  ), auto_unbox = TRUE
)

post_data_to_firestore(
  path = paste0(endpoint, "/House2/Floor1", "?documentId=", "Ground"),
  data = data_list,
  auth_token = accessTokenu
)

This creates House2 which is a non-existent document according to firestore. I understand that all I have created here is only Ground that contains Name:

Question

How do I change my POST request to ensure that I properly create documents so that I can query them?