Did you check the purity, isolated the (at least the major) product in its pure form (HPLC or GC confirmed) and characterised the product? Your query can be dealt more precisely afterwards! The physical form change of product(s) involves many factors including, the number of components in the mixture, chemical structures of the components of the mixture and the structure of the major product of the mixture, as well as any (unwanted also!) polymerization!

first you check its TLC . Sometimes instead of chalcone  you can get polymerised product also, so it depends on how much amount you have taken starting materials.

It may be, NaOH is very strong base. Try use as the catalyst Ce(III) compound, for example see

https://www.researchgate.net/publication/268153751_One-Pot_Syntheses_Using_Carbonyl_Compounds_Catalyzed_by_CeIII_Supported_on_a_Weakly_Acidic_Cation-Exchanger_Resin

https://www.researchgate.net/publication/276059289_Kabachnik-Fields_and_Prins-Ritter_Synthesis_Application_of_CeIII_Supported_on_a_Weakly_Acidic_Cation-exchanger_Resin_in_Comparative_Study

https://www.researchgate.net/publication/267390365_Comparative_Studies_of_Catalytic_Application_of_CeriumIII_Chloride_and_Resin_Supported_CeriumIII_in_Domino_Syntheses_of_15-Benzodiazepine_and_13-Diazine_Skeletons

Article Comparative Studies of Catalytic Application of Cerium(III) ...

Conference Paper One-Pot Syntheses Using Carbonyl Compounds Catalyzed by Ce(I...

Article Kabachnik-Fields and Prins-Ritter Synthesis: Application of ...

It would be good to check your product(s), may be  on TLC or preferably GC since your product is oil, hopefully, is also volatile at early/mid temp range. The polymer won't be supported on TLC  or GC. After the first experimental run of the synthesis, you need to know the fate to decide which way to go! You may find some interesting chemistry, who knows! (although extensive chalcone chemistry is now known!). It would be very advisable to proceed further on choosing a synthesis after the analysis of the first experimental efforts! The base, reaction conditions (simple chalcone like yours do not require harsh condition- RT (Room Temperature) stirring or slight heating produces the product under mild base's influence) and catalysts will play the major role. Catalysts, especially rare-earth, are costly and many times the product purification requires extra efforts. 

In few cases oil like material are separated during chalcone synthesis. few scientist kept it overnight and got solid product.

few tried to purified it using flash column or column chromatography.

It may be due to solvent or may be impurities.

to avoid solvent, many people synthesis chalcones in absence of solvent and found the reaction (a very simple procedure, by grinding using porcelain mortar and pestle) to be highly efficient (very fast), high yield, reduction of waste, etc.

try it out.

If raw materials are solids, the chalcone product, in all probability, will be solid! High MW (Molecular Weight) chalcones also tend to be solid! The non-solvent and mechanical synthesis has its own limitations in synthesis protocol and yields. Not all preparations are feasible for solvent-less and mechanical, microwave, grinding etc. formats of energy providers for the reaction.  

Try rubbing the oil with ether it used to work for me.

Due to impurities your chalcone is liquid. Hence, wash the oily product with aq. sodium meta bisulfite and then with aq. sodium bicarbonate. It will remove the unreacted starting material. Then cool the compound in ice it will get solidified.  

Ether trituration and washings may help to crystallize the purified product if that's not polymerized!

May be because of little excess of aldehyde you might have got the oily product. Try doing this technique. To the acetyl naphthale in alocholic NaOH go on adding equimolar aldehyde dropwise. You may get yellow solid. You can recrystallize using dioxan and methanol (1:1) mixture.

The presence of formyl group activates C-F bond for aromatic nucleophilic substitution by hydroxide anion and it can complicated constitution of all product.

 Speculations need to rest, after product/non-product confirmation. All ways leading to try! Give it a try, any one!