Selles had guided Reading to sixth in League One despite their off-field concerns when he left for East Yorkshire on 6 December.
Predecessor Walter had been relieved of his duties the previous week after a run of nine matches without a win.
Selles claimed his first win as Tigers boss with a 2-1 home victory over Swansea on 21 December to end a winless run of 13 matches.
Although they claimed notable results away from home under Selles, including wins at promotion-chasing Sheffield United and Sunderland, they found home wins incredibly hard to come by and ended the season with the worst home record in the division.
Defeats at the MKM Stadium by fellow strugglers Luton and Derby meant they went into the final game of the season in the Championship relegation zone.
Other fixtures meant a win would guarantee their survival and, although they were pegged back at Fratton Park after Matt Crooks had given them the lead, a point proved to be enough to keep them up on goal difference.
After the match Selles told BBC Radio Humberside: “Everyone in the club managed difficult moments and it has been a tough season for everyone and we deserved to stay in the division.
“We had a team that was rock bottom and to achieve the target this season with all the injuries and everything else is just massive.
“Now it’s over and we crossed the line, we can rest a little bit and I told the players that we will remember this day for years to come.”
