Thanks to Cherry-picked products recommendation, you can decide to always display the same products based on productIDs and order of productIDs. Remember to verify that products are in stock, since even manual merchandising adheres to availability status.
Here are the steps to do it:
Page type: select "Other page type" --> "Other page type" (even if you want it on your front or product page, it doesn't matter as long as your placement is showing on the desired page).
Recommendation type: select "Cherry-picked recommendations"
Continue with the configuration of the recommendation and save it
Re-edit your recommendation and add the desired product IDs in the following format: