The Canadian men open Nov. 15 in Olomouc against No. 27 Czechs before taking on No. 30 Slovenia in Celje on Nov. 29.
Canada, currently ranked a career-low No. 111, is coming off a 3-0 defeat to No. 57 Australia earlier this month in London.
The loss stretched Canada's winless streak to 12 games (0-9-3) during which time it has been outscored 24-2. The Canadians haven't scored in their last eight outings, a drought that now stands at 12 hours 32 minutes.
"From here to the first official games (World Cup qualifying matches), it's important to focus on our level of play," Floro said in a statement Friday. "It is necessary to pay attention in how we defend and attack so for me the best result is to take it step by step to improve our level."
It's the first call-up for the 21-year-old Ouimette, who scored his first MLS goal on Oct. 19 to give the Impact a 2-1 victory over the Philadelphia Union. The 84th-minute goal snapped a six-game Montreal winless run.
Ouimette, a graduate of the Impact's academy who played for Canada's under-17 team, appeared in seven games (six starts) in his second MLS season.
The Czechs missed out on World Cup qualifying, finishing third in their group behind Italy and Denmark with a 4-3-3 record. Slovenia (5-5-0) placed third in its pool behind Switzerland and Iceland
Floro will be missing three key players to injury in Atiba Hutchinson, Julian de Guzman and David Edgar.
The 22-man roster features eight MLS players and three unattached (Dwayne De Rosario, Issey Nakajima-Farran and Stefan Cebara).
D.C. United declined its option last month on the 35-year-old De Rosario, a former MLS MVP.
Toronto FC is represented by defenders Ashtone Morgan and Doneil Henry and midfielders Jonathan Osorio and Kyle Bekker. Midfielder Russell Teibert carries the Vancouver Whitecaps colours.
The other MLS players are defender Nana Attakora of the San Jose Earthquakes and midfielder Kyle Porter of D.C. United.
The Canadian roster does not include Portland midfielder Will Johnson, as the Timbers are in the midst of the MLS playoffs.
While Floro continues to showcase young talent, the MLS players will be coming to camp on several weeks off. Only Montreal's Ouimette made the playoffs and that run lasted just one game. The regular season ended Oct. 27.
Canada will be based out of Bad Waltersdorf, Austria, around the European friendlies.
Goalkeepers: Lars Hirschfeld, Valerenga Fotball (Norway), Kenny Stamatopoulos, AIK (Sweden).
Defenders: Nik Ledgerwood, Hammarby (Sweden); Ashtone Morgan, Toronto FC; Andre Hainault, VfR Aalen (Germany); Adam Straith, Wehen Wiesbaden (Germany); Nana Attakora, San Jose Earthquakes; Doneil Henry, Toronto FC; Marcel de Jong, FC Augsburg (Germany); Karl W. Ouimette, Montreal Impact.
Midfielders: Pedro Pacheco, CD Santa Clara (Portugal); Kyle Bekker, Toronto FC; Russell Teibert, Vancouver Whitecaps; Samuel Piette, Fortuna Dusseldorf (Germany); Jonathan Osorio, Toronto FC; Stefan Cebara, unattached.
Midfielder-Forwards: Tosaint Ricketts, Bucaspor (Turkey), Simeon Jackson, Eintracht Braunschweig (Germany); Kyle Porter, D.C. United; Issey Nakajima-Farran, unattached.
Forwards: Iain Hume, Preston North End (England); Dwayne De Rosario, unattached.