Initially I do by iterate the JSON object get the key and value out, do concatenation with dot between keys and then pass to the matchquery.
Could you give us an example of your query please?
I'm hoping you've read the manual: https://www.elastic.co/guide/en/elasticsearch/reference/6.2/search-request-body.html
Or if you want to load a file, say from the command line:
$ curl -XPOST 'http://jfblouvmlxecs01:9200/test/_doc/1' -d @lane.json
Check this out:
p.s. Google is your friend