The easiest method: Use ketone (eg. acetophenone) (10 mmol) and aldehyde (10 mmol) in ethanol (15 ml) and add 60% NaOH (2.8 ml) solution in ice cold condition drop wise with continuous stirring for 30 min. Stir the reaction mixture for additional 2-3 h at rt. Check TLC. Then do workup.
Ref: Tetrahedron Lett. 2003, 44, 171
Only 3% ethanolic NaOH can do the reaction by shaking or stirring at ambient temperature
See this reference:
Perozo-Rondon E, Martin Aranda RM, Casal B, Duran-Valle CJ, Lau WN, Zhang XF, Yeung KL,
Catalysis Today,
114: 183-187 (2006).
Also, see the attached article.
You can try different concentrations of sod bicarb aqueous solution starting by 10 %,and stirring at ambient temperature for 2-4 hours, I believe chalcone could be formed if the reactants have moderate degree of lipophilicity. try and tell me your results.