The key with forcing bulbs is to create a lengthy period of cold before you want them to start growing. Spring-blooming bulbs that you keep in the ground all year (or plant in fall) go through such a phase in winter before waking up, after all. You can create the same effect by keeping bulbs in the refrigerator a few weeks before bringing them out to standard room temperature.
Or, you can do it the "oops" way. Let me explain:
Last spring I removed bulbs from a garden bed where I later planted vegetables, with the intention to put those bulbs back in the ground in the fall. I didn't get around to that task before snow and freezes came. The bulbs remained in a covered area on my patio. When I discovered them while cleaning last week, the bulbs' green shoots were just emerging. I could have put them in the ground, but because I had new uses in mind for their previous space, I decided to bring them indoors instead.
I used vessels from my kitchen: cake pans and a pottery roasting dish. I put a layer of gravel (found in my yard) in the bottom of each dish, with just enough water to cover the rocks. I packed the bulbs as tightly as possible, first removing papery skins (these, when wet, can lead to rot). I check every few days to adjust the water level. Ideally the bulb roots go down in the rocks, but the bulbs themselves do not get soggy. Less than a week after doing this some of the bulbs have sprouted five inches. As the leaves and stems grow taller I will wrap a ribbon around the group to keep them upright.
This shows the root growth in six days:
Other seasons I have grown bulbs inside pots with soil, but the water-only method this time around intrigues my children and visitors to my home. It makes me laugh that the clear sight of green spikes notwithstanding, adults ask incredulously, "Can they really grow like that?"