I have experience and success with oral JWH-018 and -081.
Sublingual on a mint carrier (infused via alcohol) was completely inactive at 5x the smoked dose.
Vegetable oil (olive, to be specific) was NOT a good idea. Dose is similar to smoking (5-10mg) but it takes WAY TOO LONG to kick in which leads to overdose situations.
If you want to do oral JWH, it must be in short to medium-chain fatty acids, like those found in milkfat or coconut oil.
Get one stick of butter, the real cow milk kind, and melt in a saucepan just as you would for making cannabutter. Keep the heat low and stir often. Don't burn it! Simmer until most of the water content has left the butter.
Add the appropriately-weighed dose of JWH. Figure 1:1 your average smoking dose, and PLEASE consider tolerance in this! Don't overdose your friends. Be sure to write down the actual dose used, and multiply by the number of squares you plan to cut.
Once the JWH powder is fully dissolved (only a minute or two of stirring) take the butter off the heat and make a box of brownies, substituting the butter for the oil that it normally calls for. Remember that the butter should be cool before you mix in the eggs, or you'll make a scramble instead of a cake

Bake as directed, cut into the number of squares you wrote down, and enjoy. Personally I use the hot butter to make a whole tray of dark chocolate fudge, which yields about 100 bite-sized squares with 10mg of JWH each.
I have found that with this method (MILKFAT!) the effects come on strong around 40 minutes in just like a true cannabrownie, but the duration depends on the specific JWH used (018 is longer than 250). Interestingly enough, it appears to work even on a full stomach.
ALWAYS LABEL ANY CONTAINER CONTAINING EDIBLE DRUGS! Two or three of these properly prepared treats will directly lead to overdose situation (whitey out, nausea, bad trip, whatever happens to you on a CB overdose)
Oh BTW the reason for the milkfat is because short chain fatty acids are sent to the liver for processing by a different enzyme than the ones that do longer chain unsaturated acids. short-chain acids are metabolized very quickly into energy for the body, so the drugs dissolved in them will be more predictably distributed to the bloodstream.