When an engine has sat for a year, a lot of the oil that was coating things has had a chance to slowly flow off the parts.  The oil system also has had plenty of time for all the oil to drain into the sump.

I suggest that you remove the spark plug and spray some Sta-Bil fogging oil into the cylinder.  This will lubricate the piston/cylinder, and you should do this before you try to start the engine.  I would also remove the timing inspection cover on the left side of the engine, and rotate the crank to help spread the oil up and down the cylinder.

Don't remove the old oil filter or drain the oil until after you have gotten it started.  If you remove the filter and put in a new one - now the oil pump has to fill the empty filter cavity and filter before it ever pumps any oil to the bearings or cam or rockers.

Remove the front valve inspection cap, and spray some oil on the cam and rockers as best you can.

The problem with running the bike on the sidestand, is that the camshaft is hollow, and oil flows through the center of the cam when the bike is running.  The oil first arrives at the intake lobe where there is a hole to allow oil to flow out to lubricate the lobe and intake rocker - next the oil flow to the exhaust cam lobe and there is another hole, and the oil flows out to lubricate the lobe and exhaust rocker.....then the oil flow out the end of the cam to lubricate the cam chain.  When the bike is at idle on the sidestand, the camshaft is leaned over to the left side, and the oil must climb uphil to lubricate the rockers.....there is very little oil flow to the cam, and it could be that all the oil never climbs high enough to reach the exhaust lobe, and all the oil flows out the intake rocker which is no the low side of the cam when the bike is on the sidestand.