According to DW's (possibly biased-- they don't seem to like Fico) summary:
Many people from the Middle East come to Slovakia in the hope of getting a universal document that will allow them to stay in the European Union. This, however, is a false hope.
"There is no such document," explained Branik. "Slovakia only issues a paper that serves as a confirmation of their stay in our country. Illegal smugglers often lie to the immigrants and tell them that this paper is valid in all EU countries. They usually end up bitterly disappointed." [...]
The confirmation document mentioned by Branik is unique among European countries and acts as a pull on illegal migrants. It was introduced in 2018 by Robert Fico's government and former Interior Minister Robert Kalinak.
What was Fico's party/government [stated] motivation at the time (2018) for introducing such a unique (according to DW) document that documents illegal migrants' passage through Slovakia?
(Slightly aside; to illustrate the [alleged] incongruity of Fico's policies--or maybe poisoned chalice passed on to the next government, DW also mentions that OLANO and Smer have accused each other of "weak anti-migration policy" and Kalinak even scuffled in the street with the next PM, Igor Matovic over the matter.)